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 Python function `solve_dp` is a recursive dynamic programming function that is used to solve a specific problem. The problem seems to be about choosing lines from a graph, where each line has a certain cost (represented by the graph), and there's a penalty for the distance since the last line was taken. The goal is to find the minimum cost of choosing a certain number of lines. The function takes three arguments: `graph`, `lines_left`, and `distance_since_last`. `graph` is a list of integers representing the cost of each line. `lines_left` is the number of lines that still need to be chosen. `distance_since_last` is the number of lines since the last line was chosen. The function returns a tuple, where the first element is the minimum cost of choosing `lines_left` lines from `graph`, and the second element is a list of indices of the chosen lines in `graph`. The function uses memoization with `@lru_cache(maxsize=None)` to store the results of previous computations and avoid redundant calculations. Now, let's convert this recursive function to an iterative one. The iterative version will use a bottom-up approach, which is typically faster and uses less memory than a top-down approach with memoization.
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 | from functools import lru_cache def solve_iterative(graph, lines_left): n = len(graph) dp = [[(1e9, []) for _ in range(n + 1)] for _ in range(lines_left + 1)] # Base cases for i in range(n + 1): dp[0][i] = (0, []) for j in range(lines_left + 1): dp[j][0] = (1e9, []) # Iterative solution for i in range(1, lines_left + 1): for j in range(1, n + 1): # option 1: don't take the line value = dp[i][j - 1] # option 2: take the line if j > i: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] + (j - 1 - 8)**2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[lines_left][n] |
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 | from functools import lru_cache def solve_iterative(graph, lines_left): n = len(graph) dp = [[(1e9, []) for _ in range(n + 1)] for _ in range(lines_left + 1)] # Base cases for i in range(n + 1): dp[0][i] = (0, []) for j in range(lines_left + 1): dp[j][0] = (1e9, []) # Iterative solution for i in range(1, lines_left + 1): for j in range(1, n + 1): # option 1: don't take the line value = dp[i][j - 1] # option 2: take the line if j > i: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] + (j - 1 - 8)**2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[lines_left][n] |
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 | from functools import lru_cache def solve_iterative(graph, lines_left): n = len(graph) dp = [[(1e9, []) for _ in range(n + 1)] for _ in range(lines_left + 1)] # Base cases for i in range(n + 1): dp[0][i] = (0, []) for j in range(lines_left + 1): dp[j][0] = (1e9, []) # Iterative solution for i in range(1, lines_left + 1): for j in range(1, n + 1): # option 1: don't take the line value = dp[i][j - 1] # option 2: take the line if j > i: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] + (j - 1 - 8)**2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[lines_left][n] 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 59, 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 defines a recursive dynamic programming function `solve_dp` that takes three arguments: `graph`, `lines_left`, and `distance_since_last`. The function is used to solve an optimization problem where the goal is to find the minimum cost of traversing a graph while following certain rules. The `graph` parameter is a list of integers representing the cost of each node in the graph. The `lines_left` parameter is an integer representing the number of lines that can still be taken. The `distance_since_last` parameter is an integer representing the distance since the last line was taken. The function returns a tuple, where the first element is the minimum cost of traversing the graph, and the second element is a list of indices representing the nodes that were taken. The function works by considering two options at each step: either take the current line or don't take it. If the current line is not taken, the function recursively calls itself with the rest of the graph and an incremented `distance_since_last`. If the current line is taken, the function recursively calls itself with the rest of the graph, one less line left, and a reset `distance_since_last`. The cost of taking the current line is the cost of the current node plus the square of the difference between the current `distance_since_last` and 8. The `@lru_cache(maxsize=None)` decorator is used to memoize the function, i.e., to store the results of previous calls to the function so that they can be reused in future calls. This significantly reduces the time complexity of the function. Here's how you can convert this recursive function to an iterative one:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | def solve_iterative(graph, lines_left): dp = [[(float('inf'), []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): distance_since_last = len(graph) - j # option 1: don't take the line if distance_since_last < 10: dp[i][j] = dp[i][j+1] # option 2: take the line if i < lines_left: sub, how = dp[i+1][j+1] sub += graph[j] + (distance_since_last - 8)**2 dp[i][j] = min(dp[i][j], (sub, how + [j])) return dp[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 | def solve_iterative(graph, lines_left): dp = [[(float('inf'), []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): distance_since_last = len(graph) - j # option 1: don't take the line if distance_since_last < 10: dp[i][j] = dp[i][j+1] # option 2: take the line if i < lines_left: sub, how = dp[i+1][j+1] sub += graph[j] + (distance_since_last - 8)**2 dp[i][j] = min(dp[i][j], (sub, how + [j])) return dp[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 | def solve_iterative(graph, lines_left): dp = [[(float('inf'), []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): distance_since_last = len(graph) - j # option 1: don't take the line if distance_since_last < 10: dp[i][j] = dp[i][j+1] # option 2: take the line if i < lines_left: sub, how = dp[i+1][j+1] sub += graph[j] + (distance_since_last - 8)**2 dp[i][j] = min(dp[i][j], (sub, how + [j])) return dp[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 51, 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 given code defines a recursive dynamic programming function `solve_dp` that tries to solve an optimization problem on a graph. The graph is represented as a list of integers, where each integer represents the cost of taking a line in the graph. The function aims to find the minimum cost of taking a certain number of lines in the graph, with a penalty for the distance since the last line taken. The function `solve_dp` takes three arguments: `graph`, `lines_left`, and `distance_since_last`. `graph` is a list of integers representing the cost of each line. `lines_left` is the number of lines that still need to be taken. `distance_since_last` is the distance since the last line was taken, which is used to calculate the penalty. The function returns a tuple, where the first element is the minimum cost of taking `lines_left` lines in the graph, and the second element is a list of indices of the lines taken in the graph. The function uses memoization with `@lru_cache(maxsize=None)` to store the results of previous computations and avoid redundant calculations. Here's an iterative version of the function, named `solve_iterative`:
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 | from collections import deque def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[0][0] = (0, []) for i in range(lines_left + 1): for j in range(len(graph) + 1): if j < i: continue if i == 0 and j == 0: continue value = (1e9, []) # option 1: don't take the line if j > 0: distance_since_last = 1 while distance_since_last < 10 and j + distance_since_last <= len(graph): if dp[i][j + distance_since_last][0] < value[0]: value = dp[i][j + distance_since_last] distance_since_last += 1 # option 2: take the line if i > 0 and j > 0: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] value = min(value, (sub, how + [j])) dp[i][j] = value 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 23 24 25 26 27 28 29 30 31 32 | from collections import deque def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[0][0] = (0, []) for i in range(lines_left + 1): for j in range(len(graph) + 1): if j < i: continue if i == 0 and j == 0: continue value = (1e9, []) # option 1: don't take the line if j > 0: distance_since_last = 1 while distance_since_last < 10 and j + distance_since_last <= len(graph): if dp[i][j + distance_since_last][0] < value[0]: value = dp[i][j + distance_since_last] distance_since_last += 1 # option 2: take the line if i > 0 and j > 0: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] value = min(value, (sub, how + [j])) dp[i][j] = value 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 57 58 59 60 61 62 63 64 65 66 | from collections import deque def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[0][0] = (0, []) for i in range(lines_left + 1): for j in range(len(graph) + 1): if j < i: continue if i == 0 and j == 0: continue value = (1e9, []) # option 1: don't take the line if j > 0: distance_since_last = 1 while distance_since_last < 10 and j + distance_since_last <= len(graph): if dp[i][j + distance_since_last][0] < value[0]: value = dp[i][j + distance_since_last] distance_since_last += 1 # option 2: take the line if i > 0 and j > 0: sub, how = dp[i - 1][j - 1] sub += graph[j - 1] value = min(value, (sub, how + [j])) dp[i][j] = value 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 64, 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 given code defines a recursive dynamic programming function `solve_dp` that tries to solve an optimization problem on a graph. The graph is represented as a list of integers, where each integer represents the cost of taking a line in the graph. The function takes three arguments: `graph`, `lines_left`, and `distance_since_last`. - `graph` is a list of integers representing the cost of each line in the graph. - `lines_left` is the number of lines that the function is allowed to take. - `distance_since_last` is the distance since the last line was taken. The function returns a tuple, where the first element is the minimum total cost of taking `lines_left` lines from the graph, and the second element is a list of indices of the lines taken in the graph. The cost of taking a line is the cost of the line plus the square of the distance since the last line was taken minus 8. The function uses memoization with the `lru_cache` decorator to store previously computed results and avoid redundant computations. Here's an iterative version of the function, named `solve_iterative`, that performs the same task:
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 | from operator import itemgetter def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): if j < i: continue # option 1: don't take the line value = (1e9, []) if j < len(graph) - 1: distance_since_last = 1 while j + distance_since_last < len(graph) and distance_since_last < 10: value = min(value, dp[i][j + distance_since_last + 1]) distance_since_last += 1 # option 2: take the line if i < lines_left: sub, how = dp[i + 1][j + 1] sub += graph[j] + (distance_since_last - 8) ** 2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[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 21 22 23 24 25 26 27 28 | from operator import itemgetter def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): if j < i: continue # option 1: don't take the line value = (1e9, []) if j < len(graph) - 1: distance_since_last = 1 while j + distance_since_last < len(graph) and distance_since_last < 10: value = min(value, dp[i][j + distance_since_last + 1]) distance_since_last += 1 # option 2: take the line if i < lines_left: sub, how = dp[i + 1][j + 1] sub += graph[j] + (distance_since_last - 8) ** 2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[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 55 56 57 58 59 60 61 62 | from operator import itemgetter def solve_iterative(graph, lines_left): dp = [[(1e9, []) for _ in range(len(graph) + 1)] for _ in range(lines_left + 1)] dp[-1][-1] = (0, []) for i in range(lines_left - 1, -1, -1): for j in range(len(graph) - 1, -1, -1): if j < i: continue # option 1: don't take the line value = (1e9, []) if j < len(graph) - 1: distance_since_last = 1 while j + distance_since_last < len(graph) and distance_since_last < 10: value = min(value, dp[i][j + distance_since_last + 1]) distance_since_last += 1 # option 2: take the line if i < lines_left: sub, how = dp[i + 1][j + 1] sub += graph[j] + (distance_since_last - 8) ** 2 value = min(value, (sub, how + [j])) dp[i][j] = value return dp[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 60, 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 given code defines a recursive dynamic programming function `solve_dp` that tries to solve an optimization problem on a graph. The graph is represented as a list of integers, where each integer represents the cost of taking a line in the graph. The function takes three arguments: `graph`, `lines_left`, and `distance_since_last`. - `graph` is a list of integers representing the cost of each line. - `lines_left` is the number of lines that are left to be taken. - `distance_since_last` is the distance since the last line was taken. The function returns a tuple, where the first element is the minimum total cost of taking `lines_left` lines from the graph, and the second element is a list of indices of the lines taken in the graph. The cost of taking a line is the cost of the line plus the square of the distance since the last line was taken minus 8. If it's not possible to take `lines_left` lines from the graph, the function returns a tuple with the first element set to 1e9. The function uses memoization with the `@lru_cache(maxsize=None)` decorator to store the results of previous computations and avoid redundant computations. Here's an iterative version of the function, named `solve_iterative`, that performs the same computation:
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 | def solve_iterative(graph, lines_left, distance_since_last): # Initialize the memoization table dp = {} for i in range(len(graph), -1, -1): for j in range(lines_left + 1): for k in range(11): dp[(i, j, k)] = (1e9, []) dp[(0, 0, 0)] = (0, []) # Iterate over the graph in reverse order for i in range(len(graph) - 1, -1, -1): for j in range(lines_left, -1, -1): for k in range(1, 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: sub, how = dp[(i + 1, j - 1, 0)] sub += graph[i] + (k - 8) ** 2 dp[(i, j, k)] = min(dp[(i, j, k)], (sub, how + [i])) return dp[(0, lines_left, distance_since_last)] |
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 | def solve_iterative(graph, lines_left, distance_since_last): # Initialize the memoization table dp = {} for i in range(len(graph), -1, -1): for j in range(lines_left + 1): for k in range(11): dp[(i, j, k)] = (1e9, []) dp[(0, 0, 0)] = (0, []) # Iterate over the graph in reverse order for i in range(len(graph) - 1, -1, -1): for j in range(lines_left, -1, -1): for k in range(1, 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: sub, how = dp[(i + 1, j - 1, 0)] sub += graph[i] + (k - 8) ** 2 dp[(i, j, k)] = min(dp[(i, j, k)], (sub, how + [i])) return dp[(0, lines_left, distance_since_last)] |
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 | def solve_iterative(graph, lines_left, distance_since_last): # Initialize the memoization table dp = {} for i in range(len(graph), -1, -1): for j in range(lines_left + 1): for k in range(11): dp[(i, j, k)] = (1e9, []) dp[(0, 0, 0)] = (0, []) # Iterate over the graph in reverse order for i in range(len(graph) - 1, -1, -1): for j in range(lines_left, -1, -1): for k in range(1, 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: sub, how = dp[(i + 1, j - 1, 0)] sub += graph[i] + (k - 8) ** 2 dp[(i, j, k)] = min(dp[(i, j, k)], (sub, how + [i])) return dp[(0, lines_left, distance_since_last)] 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 59, in <module>
assert answer == expected, f'Wrong answer; got {answer} instead of {expected}'
^^^^^^^^^^^^^^^^^^
AssertionError: Wrong answer; got (1000000000.0, []) instead of (171, [3, 11, 20, 30, 36, 44, 51, 59, 69, 79, 90, 100])
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True