Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
This code is a recursive function that solves a dynamic programming problem. It appears to be related to some kind of optimization problem involving a graph and a set of "lines" that can be taken or not taken. Here's what the code does: 1. The `@lru_cache(maxsize=None)` decorator is used to cache the results of the function calls, which can significantly improve the performance of recursive functions by avoiding redundant computations. 2. The `solve_dp` function takes three arguments: - `graph`: a list or sequence representing the graph - `lines_left`: an integer representing the number of lines that can still be taken - `distance_since_last`: an integer representing the distance from the last taken line 3. The function first checks two base cases: - If the length of the `graph` is less than `lines_left`, it means there aren't enough lines to take, so it returns a large value (`1e9`) and an empty list. - If `lines_left` is 0 and the `graph` is empty, it means all lines have been taken, so it returns 0 and an empty list. 4. If neither base case is met, the function explores two options: - Option 1: Don't take the current line. In this case, it recursively calls `solve_dp` with the remaining graph (`graph[1:]`), the same `lines_left`, and `distance_since_last` incremented by 1. However, this option is only considered if `distance_since_last` is less than 10. - Option 2: Take the current line. In this case, it recursively calls `solve_dp` with the remaining graph (`graph[1:]`), `lines_left` decremented by 1, and `distance_since_last` reset to 0. Additionally, it adds the value of the current line (`graph[0]`) and a penalty term that depends on `distance_since_last` and the constant 8. 5. The function returns the minimum of the two options, which is a tuple containing the value and the list of taken lines (represented by their indices in the original graph). Now, let's convert this recursive function to an iterative one, making explicit the cubic work that's being done:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(lines_left + 1)] dp[0][0][0] = 0, [] for i in range(lines_left + 1): for j in range(n + 1): for k in range(11): if j < n: # Option 1: Don't take the line if k < 10: dp[i][j + 1][k + 1] = min(dp[i][j + 1][k + 1], dp[i][j][k]) # Option 2: Take the line if i < lines_left: value, path = dp[i + 1][j + 1][0] value += graph[j] + (k - 8) ** 2 path = path + [j] dp[i][j][k] = min(dp[i][j][k], (value, path)) return dp[0][n][0] |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(lines_left + 1)] dp[0][0][0] = 0, [] for i in range(lines_left + 1): for j in range(n + 1): for k in range(11): if j < n: # Option 1: Don't take the line if k < 10: dp[i][j + 1][k + 1] = min(dp[i][j + 1][k + 1], dp[i][j][k]) # Option 2: Take the line if i < lines_left: value, path = dp[i + 1][j + 1][0] value += graph[j] + (k - 8) ** 2 path = path + [j] dp[i][j][k] = min(dp[i][j][k], (value, path)) return dp[0][n][0] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(lines_left + 1)] dp[0][0][0] = 0, [] for i in range(lines_left + 1): for j in range(n + 1): for k in range(11): if j < n: # Option 1: Don't take the line if k < 10: dp[i][j + 1][k + 1] = min(dp[i][j + 1][k + 1], dp[i][j][k]) # Option 2: Take the line if i < lines_left: value, path = dp[i + 1][j + 1][0] value += graph[j] + (k - 8) ** 2 path = path + [j] dp[i][j][k] = min(dp[i][j][k], (value, path)) return dp[0][n][0] answer = 0 import random mylist = list(range(100)) random.shuffle(mylist) from functools import lru_cache @lru_cache(maxsize=None) def my_solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, my_solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = my_solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value answer = solve_iterative(tuple(mylist), len(mylist)//8, 4) expected = my_solve_dp(tuple(mylist), len(mylist)//8, 4) assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
Traceback (most recent call last):
File "/usr/src/app/main.py", line 53, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: solve_iterative() takes 2 positional arguments but 3 were given
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
The provided code is a recursive function that solves a problem related to graph traversal or path finding. The function takes three arguments: 1. `graph`: A list representing the graph or the path that needs to be traversed. 2. `lines_left`: The number of lines (or edges) that can be taken. 3. `distance_since_last`: The distance since the last line was taken. The function uses dynamic programming with memoization (caching) to avoid redundant computations. The `@lru_cache(maxsize=None)` decorator stores the results of previously computed function calls with the same arguments, allowing the function to reuse those results instead of recomputing them. The function recursively explores two options: 1. **Don't take the line**: If the distance since the last line was taken is less than 10, it compares the current value with the result of skipping the current line and recursively calling the function with the remaining graph, the same number of lines left, and an incremented distance since the last line. 2. **Take the line**: If there are lines left to take, it recursively calls the function with the remaining graph, one fewer line left, and a reset distance since the last line. It computes the cost of taking the current line by adding the value of the current line to the squared difference between the distance since the last line and 8. The function then compares the current value with the sum of the recursive result and the computed cost. The function returns the minimum value and the corresponding path (represented as a list of indices) between the two options. Here's the iterative version of the function, named `solve_iterative`, which performs the same computation but using an iterative approach:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | from collections import deque def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) if n < lines_left: return 1e9, [] if lines_left == 0 and n == 0: return 0, [] queue = deque([(0, lines_left, distance_since_last, [])]) best_value, best_path = 1e9, [] while queue: value, lines_left, distance_since_last, path = queue.popleft() if value >= best_value: continue if lines_left == 0 and len(graph) == 0: best_value, best_path = value, path continue # option 1: don't take the line new_distance = distance_since_last + 1 if new_distance < 10: new_value = value new_path = path[:] queue.append((new_value, lines_left, new_distance, new_path)) # option 2: take the line if lines_left > 0: new_value = value + graph[0] + (distance_since_last - 8) ** 2 new_path = path[:] + [len(graph)] queue.append((new_value, lines_left - 1, 0, new_path)) graph = graph[1:] return best_value, best_path |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | from collections import deque def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) if n < lines_left: return 1e9, [] if lines_left == 0 and n == 0: return 0, [] queue = deque([(0, lines_left, distance_since_last, [])]) best_value, best_path = 1e9, [] while queue: value, lines_left, distance_since_last, path = queue.popleft() if value >= best_value: continue if lines_left == 0 and len(graph) == 0: best_value, best_path = value, path continue # option 1: don't take the line new_distance = distance_since_last + 1 if new_distance < 10: new_value = value new_path = path[:] queue.append((new_value, lines_left, new_distance, new_path)) # option 2: take the line if lines_left > 0: new_value = value + graph[0] + (distance_since_last - 8) ** 2 new_path = path[:] + [len(graph)] queue.append((new_value, lines_left - 1, 0, new_path)) graph = graph[1:] return best_value, best_path |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | from collections import deque def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) if n < lines_left: return 1e9, [] if lines_left == 0 and n == 0: return 0, [] queue = deque([(0, lines_left, distance_since_last, [])]) best_value, best_path = 1e9, [] while queue: value, lines_left, distance_since_last, path = queue.popleft() if value >= best_value: continue if lines_left == 0 and len(graph) == 0: best_value, best_path = value, path continue # option 1: don't take the line new_distance = distance_since_last + 1 if new_distance < 10: new_value = value new_path = path[:] queue.append((new_value, lines_left, new_distance, new_path)) # option 2: take the line if lines_left > 0: new_value = value + graph[0] + (distance_since_last - 8) ** 2 new_path = path[:] + [len(graph)] queue.append((new_value, lines_left - 1, 0, new_path)) graph = graph[1:] return best_value, best_path answer = 0 import random mylist = list(range(100)) random.shuffle(mylist) from functools import lru_cache @lru_cache(maxsize=None) def my_solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, my_solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = my_solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value answer = solve_iterative(tuple(mylist), len(mylist)//8, 4) expected = my_solve_dp(tuple(mylist), len(mylist)//8, 4) assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
Traceback (most recent call last):
File "/usr/src/app/main.py", line 70, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/src/app/main.py", line 33, in solve_iterative
new_value = value + graph[0] + (distance_since_last - 8) ** 2
~~~~~^^^
IndexError: tuple index out of range
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
This code appears to be a recursive function written in Python that solves a dynamic programming problem related to a graph. The function `solve_dp` takes three arguments: 1. `graph`: This is likely a list or array representing the graph or problem instance. 2. `lines_left`: An integer representing the number of lines or edges that can still be added or taken. 3. `distance_since_last`: An integer representing the distance or steps since the last line or edge was taken. The function uses dynamic programming and memoization (via the `@lru_cache` decorator) to solve the problem efficiently by storing and reusing previously computed results. Here's what the function does: 1. It checks base cases: - If there are not enough nodes left in the graph to accommodate the remaining `lines_left`, it returns a very large value (1e9) and an empty list, indicating an invalid or infeasible solution. - If there are no lines left to take and no nodes left in the graph, it returns 0 and an empty list, indicating a valid solution with no cost. 2. It explores two options: - Option 1: Don't take the current line or edge. In this case, it recursively calls `solve_dp` with the remaining graph (`graph[1:]`), the same `lines_left`, and increments `distance_since_last` by 1. - Option 2: Take the current line or edge if there are lines left. It recursively calls `solve_dp` with the remaining graph (`graph[1:]`), decrements `lines_left` by 1, and resets `distance_since_last` to 0. It also adds the cost of taking the current line or edge, which is computed as `graph[0] + (distance_since_last-8)**2`. 3. The function returns the minimum value and the corresponding list of indices (representing the lines or edges taken) between the two options. Now, let's convert this recursive function to an iterative one, making explicit the cubic work that's being done:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | from collections import deque def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n+1)] dp[n][0] = [0, []] for i in range(n-1, -1, -1): for j in range(lines_left+1): for k in range(11): # option 1: don't take the line if k < 10: dp[i][j][k] = min(dp[i][j][k], dp[i+1][j][k+1]) # option 2: take the line if j > 0: cost, path = dp[i+1][j-1][0] cost += graph[i] + (k-8)**2 path = path + [i] dp[i][j][k] = min(dp[i][j][k], [cost, path]) return dp[0][lines_left][0] |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | from collections import deque def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n+1)] dp[n][0] = [0, []] for i in range(n-1, -1, -1): for j in range(lines_left+1): for k in range(11): # option 1: don't take the line if k < 10: dp[i][j][k] = min(dp[i][j][k], dp[i+1][j][k+1]) # option 2: take the line if j > 0: cost, path = dp[i+1][j-1][0] cost += graph[i] + (k-8)**2 path = path + [i] dp[i][j][k] = min(dp[i][j][k], [cost, path]) return dp[0][lines_left][0] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 | from collections import deque def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n+1)] dp[n][0] = [0, []] for i in range(n-1, -1, -1): for j in range(lines_left+1): for k in range(11): # option 1: don't take the line if k < 10: dp[i][j][k] = min(dp[i][j][k], dp[i+1][j][k+1]) # option 2: take the line if j > 0: cost, path = dp[i+1][j-1][0] cost += graph[i] + (k-8)**2 path = path + [i] dp[i][j][k] = min(dp[i][j][k], [cost, path]) return dp[0][lines_left][0] answer = 0 import random mylist = list(range(100)) random.shuffle(mylist) from functools import lru_cache @lru_cache(maxsize=None) def my_solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, my_solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = my_solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value answer = solve_iterative(tuple(mylist), len(mylist)//8, 4) expected = my_solve_dp(tuple(mylist), len(mylist)//8, 4) assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
Traceback (most recent call last):
File "/usr/src/app/main.py", line 54, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: solve_iterative() takes 2 positional arguments but 3 were given
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
This code is a recursive function that solves a dynamic programming problem. The function `solve_dp` takes three arguments: 1. `graph`: A list representing a graph, where each element is a value associated with a node or line. 2. `lines_left`: An integer representing the number of lines that can still be taken. 3. `distance_since_last`: An integer representing the distance since the last line was taken. The function returns a tuple containing two values: 1. The minimum cost or value associated with the remaining graph and lines. 2. A list representing the indices of the lines taken to achieve the minimum cost. The function works by exploring two options: 1. Not taking the current line: In this case, the function recursively calls itself with the remaining graph (`graph[1:]`) and increments `distance_since_last` by 1. 2. Taking the current line: If there are lines left (`lines_left > 0`), the function recursively calls itself with the remaining graph (`graph[1:]`), decrements `lines_left` by 1, and resets `distance_since_last` to 0. It also adds the cost of taking the current line, which is the value of the current node (`graph[0]`) plus a penalty based on the distance since the last line was taken (`(distance_since_last-8)**2`). The function uses memoization (caching) with the `@lru_cache` decorator to avoid recomputing the same subproblems multiple times. Here's the iterative version of the function, called `solve_iterative`:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n + 1)] dp[0][0][0] = 0, [] for i in range(n): for j in range(lines_left + 1): for k in range(11): # option 1: don't take the line if k < 10: dp[i + 1][j][k + 1] = min(dp[i + 1][j][k + 1], dp[i][j][k]) # option 2: take the line if j < lines_left: sub, how = dp[i][j + 1][0] sub += graph[i] + (k - 8) ** 2 new_how = how + [i] dp[i + 1][j + 1][0] = min(dp[i + 1][j + 1][0], (sub, new_how)) return dp[n][0][0] |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n + 1)] dp[0][0][0] = 0, [] for i in range(n): for j in range(lines_left + 1): for k in range(11): # option 1: don't take the line if k < 10: dp[i + 1][j][k + 1] = min(dp[i + 1][j][k + 1], dp[i][j][k]) # option 2: take the line if j < lines_left: sub, how = dp[i][j + 1][0] sub += graph[i] + (k - 8) ** 2 new_how = how + [i] dp[i + 1][j + 1][0] = min(dp[i + 1][j + 1][0], (sub, new_how)) return dp[n][0][0] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(11)] for _ in range(n + 1)] dp[0][0][0] = 0, [] for i in range(n): for j in range(lines_left + 1): for k in range(11): # option 1: don't take the line if k < 10: dp[i + 1][j][k + 1] = min(dp[i + 1][j][k + 1], dp[i][j][k]) # option 2: take the line if j < lines_left: sub, how = dp[i][j + 1][0] sub += graph[i] + (k - 8) ** 2 new_how = how + [i] dp[i + 1][j + 1][0] = min(dp[i + 1][j + 1][0], (sub, new_how)) return dp[n][0][0] answer = 0 import random mylist = list(range(100)) random.shuffle(mylist) from functools import lru_cache @lru_cache(maxsize=None) def my_solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, my_solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = my_solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value answer = solve_iterative(tuple(mylist), len(mylist)//8, 4) expected = my_solve_dp(tuple(mylist), len(mylist)//8, 4) assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
Traceback (most recent call last):
File "/usr/src/app/main.py", line 52, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: solve_iterative() takes 2 positional arguments but 3 were given
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
Explain what this code does. Then, convert this recursive function to an iterative one, making explicit the cubic work that's being done. The functions should return exactly the same output but the iterative one should be faster. Call your function `solve_iterative` and match the type signature of the original function. @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value
This code is a recursive dynamic programming solution to a problem that involves finding the optimal way to build subway lines on a graph. Here's what the code does: 1. The `solve_dp` function takes three arguments: - `graph`: a list representing the graph (presumably the cost of building a line between nodes) - `lines_left`: the number of lines that can still be built - `distance_since_last`: the distance since the last line was built 2. The function uses memoization (`@lru_cache`) to store and reuse previously computed results, improving efficiency. 3. The base cases are: - If there are not enough nodes left in the graph to build the remaining lines, return a very large value (1e9) as the cost and an empty list as the solution. - If no lines are left to build and the graph is empty, return 0 as the cost and an empty list as the solution (since the problem is solved). 4. If the base cases don't apply, the function considers two options: - Option 1: Don't take the current line. In this case, the function recursively calls itself with the remaining graph (`graph[1:]`), the same number of lines left (`lines_left`), and an incremented `distance_since_last`. - Option 2: Take the current line. If there are lines left to build, the function recursively calls itself with the remaining graph (`graph[1:]`), one fewer line left (`lines_left-1`), and `distance_since_last` reset to 0. The cost of taking this line is added to the recursive result, which includes the cost of the line itself (`graph[0]`) and a penalty based on the distance since the last line was built (`(distance_since_last-8)**2`). 5. The function returns the minimum cost and the corresponding solution (a list of indices representing the lines to take). Here's the iterative version of the function, which should be faster than the recursive version:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(n+1)] for _ in range(lines_left+1)] dp[0][n] = [0, []] # Base case: no lines left, empty graph for l in range(lines_left, -1, -1): for i in range(n-1, -1, -1): # Option 1: Don't take the line cost, path = dp[l][i+1] if i < n-1: new_cost, new_path = min((cost, path), dp[l][i]) # Option 2: Take the line if l < lines_left: sub_cost, sub_path = dp[l+1][i+1] new_cost = sub_cost + graph[i] + (max(0, i - sub_path[-1]) - 8)**2 if sub_path else 1e9 new_path = sub_path + [i] new_cost, new_path = min((new_cost, new_path), (cost, path), key=lambda x: x[0]) dp[l][i] = [new_cost, new_path] return dp[lines_left][0] |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(n+1)] for _ in range(lines_left+1)] dp[0][n] = [0, []] # Base case: no lines left, empty graph for l in range(lines_left, -1, -1): for i in range(n-1, -1, -1): # Option 1: Don't take the line cost, path = dp[l][i+1] if i < n-1: new_cost, new_path = min((cost, path), dp[l][i]) # Option 2: Take the line if l < lines_left: sub_cost, sub_path = dp[l+1][i+1] new_cost = sub_cost + graph[i] + (max(0, i - sub_path[-1]) - 8)**2 if sub_path else 1e9 new_path = sub_path + [i] new_cost, new_path = min((new_cost, new_path), (cost, path), key=lambda x: x[0]) dp[l][i] = [new_cost, new_path] return dp[lines_left][0] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 | def solve_iterative(graph, lines_left): n = len(graph) dp = [[[1e9, []] for _ in range(n+1)] for _ in range(lines_left+1)] dp[0][n] = [0, []] # Base case: no lines left, empty graph for l in range(lines_left, -1, -1): for i in range(n-1, -1, -1): # Option 1: Don't take the line cost, path = dp[l][i+1] if i < n-1: new_cost, new_path = min((cost, path), dp[l][i]) # Option 2: Take the line if l < lines_left: sub_cost, sub_path = dp[l+1][i+1] new_cost = sub_cost + graph[i] + (max(0, i - sub_path[-1]) - 8)**2 if sub_path else 1e9 new_path = sub_path + [i] new_cost, new_path = min((new_cost, new_path), (cost, path), key=lambda x: x[0]) dp[l][i] = [new_cost, new_path] return dp[lines_left][0] answer = 0 import random mylist = list(range(100)) random.shuffle(mylist) from functools import lru_cache @lru_cache(maxsize=None) def my_solve_dp(graph, lines_left, distance_since_last): if len(graph) < lines_left: return 1e9, [] if lines_left == 0 and len(graph) == 0: return 0, [] # option 1: don't take the line value = (1e9, []) if distance_since_last < 10: value = min(value, my_solve_dp(graph[1:], lines_left, distance_since_last+1)) # option 2: take the line if lines_left > 0: sub, how = my_solve_dp(graph[1:], lines_left-1, 0) sub += graph[0] + (distance_since_last-8)**2 value = min(value, (sub, how + [len(graph)])) return value answer = solve_iterative(tuple(mylist), len(mylist)//8, 4) expected = my_solve_dp(tuple(mylist), len(mylist)//8, 4) assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
Traceback (most recent call last):
File "/usr/src/app/main.py", line 54, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: solve_iterative() takes 2 positional arguments but 3 were given
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True