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
Let me explain the code and then provide an iterative version: Explanation: This code implements a dynamic programming solution to optimize line placement in a graph. The function `solve_dp` takes three parameters: 1. `graph`: A list representing the graph, where each element is the value of a node. 2. `lines_left`: The number of lines that can still be placed. 3. `distance_since_last`: The distance since the last placed line. The function recursively explores two options at each step: 1. Don't take the current line (if the distance since the last line is less than 10). 2. Take the current line (if there are lines left to place). It uses memoization (@lru_cache) to avoid redundant calculations. The function returns a tuple containing the minimum value achieved and the list of line positions. Here's an iterative version of the function:
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 | from functools import lru_cache def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Iterate through the graph for i in range(1, n + 1): new_dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: new_dp[j][k + 1] = min(new_dp[j][k + 1], dp[j][k], key=lambda x: x[0]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8)**2 if sub < new_dp[j][0][0]: new_dp[j][0] = [sub, how + [i]] dp = new_dp return min(dp[lines_left], key=lambda x: x[0]) # Wrapper function to maintain the same interface as the original function @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, 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 26 27 28 29 30 31 32 33 34 35 | from functools import lru_cache def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Iterate through the graph for i in range(1, n + 1): new_dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: new_dp[j][k + 1] = min(new_dp[j][k + 1], dp[j][k], key=lambda x: x[0]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8)**2 if sub < new_dp[j][0][0]: new_dp[j][0] = [sub, how + [i]] dp = new_dp return min(dp[lines_left], key=lambda x: x[0]) # Wrapper function to maintain the same interface as the original function @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, 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 60 61 62 63 64 65 66 67 68 69 | from functools import lru_cache def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Iterate through the graph for i in range(1, n + 1): new_dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: new_dp[j][k + 1] = min(new_dp[j][k + 1], dp[j][k], key=lambda x: x[0]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8)**2 if sub < new_dp[j][0][0]: new_dp[j][0] = [sub, how + [i]] dp = new_dp return min(dp[lines_left], key=lambda x: x[0]) # Wrapper function to maintain the same interface as the original function @lru_cache(maxsize=None) def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, 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 69, in <module>
assert answer == expected, f'Wrong answer; got {answer} instead of {expected}'
AssertionError: Wrong answer; got [inf, []] instead of (189, [5, 9, 16, 26, 35, 43, 50, 60, 70, 77, 87, 96])
Testing if the previous output contains the string All tests passed
: False
Resulting in output: False
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
Let's break this down and then convert it to an iterative function: 1. Explanation of the original code: This is a dynamic programming solution to a problem that involves selecting lines from a graph while minimizing a cost function. The function takes three parameters: - `graph`: A list of values representing the graph - `lines_left`: The number of lines that can still be selected - `distance_since_last`: The distance since the last selected line The function uses recursion to explore two options at each step: 1. Don't take the current line (if the distance since the last line is less than 10) 2. Take the current line (if there are lines left to take) It then returns the minimum cost and the list of selected line indices. The `@lru_cache(maxsize=None)` decorator is used for memoization to avoid redundant computations. 2. Iterative version: Here's an iterative version of the function that explicitly shows the cubic work being done:
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] # Base case if n == 0 and lines_left == 0: return 0, [] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i == 0 and j == 0: dp[j][k] = [0, []] elif i == 0: dp[j][k] = [float('inf'), []] else: # Option 1: don't take the line if k < 10: dp[j][k] = min(dp[j][k], dp[j][(k + 1) % 11]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8) ** 2 new_value = (sub, how + [i]) dp[j][k] = min(dp[j][k], new_value) # Find the minimum value in the last row result = min(dp[lines_left]) return result |
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] # Base case if n == 0 and lines_left == 0: return 0, [] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i == 0 and j == 0: dp[j][k] = [0, []] elif i == 0: dp[j][k] = [float('inf'), []] else: # Option 1: don't take the line if k < 10: dp[j][k] = min(dp[j][k], dp[j][(k + 1) % 11]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8) ** 2 new_value = (sub, how + [i]) dp[j][k] = min(dp[j][k], new_value) # Find the minimum value in the last row result = min(dp[lines_left]) return result |
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] # Base case if n == 0 and lines_left == 0: return 0, [] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i == 0 and j == 0: dp[j][k] = [0, []] elif i == 0: dp[j][k] = [float('inf'), []] else: # Option 1: don't take the line if k < 10: dp[j][k] = min(dp[j][k], dp[j][(k + 1) % 11]) # Option 2: take the line if j > 0: sub, how = dp[j - 1][0] sub += graph[i - 1] + (k - 8) ** 2 new_value = (sub, how + [i]) dp[j][k] = min(dp[j][k], new_value) # Find the minimum value in the last row result = min(dp[lines_left]) return result 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 66, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
File "/usr/src/app/main.py", line 30, in solve_iterative
dp[j][k] = min(dp[j][k], new_value)
TypeError: '<' not supported between instances of 'tuple' and 'list'
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
Let's break this down and then convert it to an iterative function: 1. Explanation of the original code: This is a dynamic programming solution to a problem involving selecting lines from a graph. The function aims to minimize a cost while selecting a certain number of lines, considering a distance constraint. - `graph`: A list of values representing the graph. - `lines_left`: The number of lines that can still be selected. - `distance_since_last`: The distance since the last selected line. The function recursively explores two options at each step: 1. Don't take the current line. 2. Take the current line (if lines are still available). It uses memoization (@lru_cache) to optimize repeated subproblems. 2. Converting to an iterative function: Here's an iterative version that explicitly shows the cubic work being done:
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 | def solve_iterative(graph, total_lines, max_distance=10): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(max_distance)] for _ in range(total_lines + 1)] # Base case: 0 cost for selecting 0 lines at the end of the graph for d in range(max_distance): dp[0][d] = [0, []] # Iterate through the graph backwards for i in range(n-1, -1, -1): for lines in range(total_lines + 1): for dist in range(max_distance): # Option 1: Don't take the line if dist < max_distance - 1: dp[lines][dist] = min(dp[lines][dist], dp[lines][dist+1]) # Option 2: Take the line if lines > 0: cost, path = dp[lines-1][0] new_cost = cost + graph[i] + (dist-8)**2 if new_cost < dp[lines][dist][0]: dp[lines][dist] = [new_cost, [n-i] + path] return dp[total_lines][0] # Wrapper function to match the original signature def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, lines_left) |
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 | def solve_iterative(graph, total_lines, max_distance=10): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(max_distance)] for _ in range(total_lines + 1)] # Base case: 0 cost for selecting 0 lines at the end of the graph for d in range(max_distance): dp[0][d] = [0, []] # Iterate through the graph backwards for i in range(n-1, -1, -1): for lines in range(total_lines + 1): for dist in range(max_distance): # Option 1: Don't take the line if dist < max_distance - 1: dp[lines][dist] = min(dp[lines][dist], dp[lines][dist+1]) # Option 2: Take the line if lines > 0: cost, path = dp[lines-1][0] new_cost = cost + graph[i] + (dist-8)**2 if new_cost < dp[lines][dist][0]: dp[lines][dist] = [new_cost, [n-i] + path] return dp[total_lines][0] # Wrapper function to match the original signature def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, lines_left) |
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 | def solve_iterative(graph, total_lines, max_distance=10): n = len(graph) # Initialize the DP table dp = [[[float('inf'), []] for _ in range(max_distance)] for _ in range(total_lines + 1)] # Base case: 0 cost for selecting 0 lines at the end of the graph for d in range(max_distance): dp[0][d] = [0, []] # Iterate through the graph backwards for i in range(n-1, -1, -1): for lines in range(total_lines + 1): for dist in range(max_distance): # Option 1: Don't take the line if dist < max_distance - 1: dp[lines][dist] = min(dp[lines][dist], dp[lines][dist+1]) # Option 2: Take the line if lines > 0: cost, path = dp[lines-1][0] new_cost = cost + graph[i] + (dist-8)**2 if new_cost < dp[lines][dist][0]: dp[lines][dist] = [new_cost, [n-i] + path] return dp[total_lines][0] # Wrapper function to match the original signature def solve_dp(graph, lines_left, distance_since_last): return solve_iterative(graph, lines_left) 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>
assert answer == expected, f'Wrong answer; got {answer} instead of {expected}'
AssertionError: Wrong answer; got [377, [97, 92, 87, 72, 62, 54, 49, 44, 38, 35, 26, 12]] instead of (167, [4, 12, 18, 26, 35, 44, 54, 62, 72, 78, 87, 97])
Testing if the previous output contains the string All tests passed
: False
Resulting in output: False
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
Certainly! Let's break this down and then convert it to an iterative function. Explanation of the original code: 1. This is a dynamic programming solution to a problem involving selecting lines from a graph. 2. It uses memoization (@lru_cache) to optimize recursive calls. 3. The function takes three parameters: - graph: Likely a list of values representing the graph - lines_left: The number of lines that can still be selected - distance_since_last: The distance since the last selected line 4. The base cases are: - If there are more lines to select than graph elements, return a large value (1e9) - If no lines are left to select and the graph is empty, return 0 5. The function explores two options: - Don't take the current line (if distance_since_last < 10) - Take the current line (if lines_left > 0) 6. It recursively calls itself for both options and chooses the minimum value 7. The function returns a tuple: (minimum value, list of selected line positions) Now, let's convert this to an iterative function:
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Fill the DP table for i in range(1, n + 1): for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: value, how = dp[j][k+1] if value < dp[j][k][0]: dp[j][k] = [value, how] # Option 2: take the line if j > 0: sub, how = dp[j-1][0] sub += graph[i-1] + (k-8)**2 if sub < dp[j][k][0]: dp[j][k] = [sub, how + [n-i+1]] return tuple(dp[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 26 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Fill the DP table for i in range(1, n + 1): for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: value, how = dp[j][k+1] if value < dp[j][k][0]: dp[j][k] = [value, how] # Option 2: take the line if j > 0: sub, how = dp[j-1][0] sub += graph[i-1] + (k-8)**2 if sub < dp[j][k][0]: dp[j][k] = [sub, how + [n-i+1]] return tuple(dp[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 60 61 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1)] for i in range(11): dp[0][i][0] = 0 if n == 0 else float('inf') # Fill the DP table for i in range(1, n + 1): for j in range(lines_left + 1): for k in range(11): # Option 1: don't take the line if k < 10: value, how = dp[j][k+1] if value < dp[j][k][0]: dp[j][k] = [value, how] # Option 2: take the line if j > 0: sub, how = dp[j-1][0] sub += graph[i-1] + (k-8)**2 if sub < dp[j][k][0]: dp[j][k] = [sub, how + [n-i+1]] return tuple(dp[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 61, in <module>
assert answer == expected, f'Wrong answer; got {answer} instead of {expected}'
AssertionError: Wrong answer; got (inf, []) instead of (173, [8, 17, 23, 32, 41, 45, 51, 61, 70, 78, 85, 95])
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
Let's break down the code and then convert it to an iterative version: 1. Explanation of the original code: This is a dynamic programming solution to a problem involving selecting lines from a graph. The function `solve_dp` takes three parameters: - `graph`: A list of values representing the graph - `lines_left`: The number of lines that can still be selected - `distance_since_last`: The distance since the last selected line The function uses recursion to explore two options at each step: 1. Don't take the current line (if the distance since the last line is less than 10) 2. Take the current line (if there are lines left to take) It uses memoization (@lru_cache) to optimize repeated subproblems. The function returns a tuple containing the minimum value achieved and a list of selected line positions. 2. Iterative version: Here's an iterative version of the function that makes the cubic work explicit:
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1) for _ in range(n + 1)] # Base case dp[0][0][distance_since_last] = [0, []] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i < n: # Option 1: Don't take the line if k < 10: new_value, new_how = dp[i][j][k] if new_value < dp[i+1][j][k+1][0]: dp[i+1][j][k+1] = [new_value, new_how[:]] # Option 2: Take the line if j > 0: new_value, new_how = dp[i][j-1][0] new_value += graph[i] + (k-8)**2 if new_value < dp[i+1][j][0][0]: dp[i+1][j][0] = [new_value, new_how + [n-i]] # Find the best result best_result = min(dp[n][lines_left]) return tuple(best_result) |
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1) for _ in range(n + 1)] # Base case dp[0][0][distance_since_last] = [0, []] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i < n: # Option 1: Don't take the line if k < 10: new_value, new_how = dp[i][j][k] if new_value < dp[i+1][j][k+1][0]: dp[i+1][j][k+1] = [new_value, new_how[:]] # Option 2: Take the line if j > 0: new_value, new_how = dp[i][j-1][0] new_value += graph[i] + (k-8)**2 if new_value < dp[i+1][j][0][0]: dp[i+1][j][0] = [new_value, new_how + [n-i]] # Find the best result best_result = min(dp[n][lines_left]) return tuple(best_result) |
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 | def solve_iterative(graph, lines_left, distance_since_last): n = len(graph) # Create a 3D DP table dp = [[[float('inf'), []] for _ in range(11)] for _ in range(lines_left + 1) for _ in range(n + 1)] # Base case dp[0][0][distance_since_last] = [0, []] # Fill the DP table for i in range(n + 1): for j in range(lines_left + 1): for k in range(11): if i < n: # Option 1: Don't take the line if k < 10: new_value, new_how = dp[i][j][k] if new_value < dp[i+1][j][k+1][0]: dp[i+1][j][k+1] = [new_value, new_how[:]] # Option 2: Take the line if j > 0: new_value, new_how = dp[i][j-1][0] new_value += graph[i] + (k-8)**2 if new_value < dp[i+1][j][0][0]: dp[i+1][j][0] = [new_value, new_how + [n-i]] # Find the best result best_result = min(dp[n][lines_left]) return tuple(best_result) 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 63, in <module>
answer = solve_iterative(tuple(mylist), len(mylist)//8, 4)
File "/usr/src/app/main.py", line 9, in solve_iterative
dp[0][0][distance_since_last] = [0, []]
IndexError: list assignment index out of range
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True