Unexpected Output in Recursive Function for Generating Permutations in Python 3.9
I'm trying to implement a recursive function to generate all permutations of a list of integers in Python 3.9. However, I'm seeing unexpected results where some permutations are repeated, and others are missing. Here’s the code I’ve written so far: ```python def permute(nums): result = [] def backtrack(start): if start == len(nums): result.append(nums[:]) # Append a copy of the current permutation return for i in range(start, len(nums)): nums[start], nums[i] = nums[i], nums[start] # Swap backtrack(start + 1) nums[start], nums[i] = nums[i], nums[start] # Swap back backtrack(0) return result nums = [1, 1, 2] print(permute(nums)) ``` I'm passing in a list with duplicate elements, specifically `[1, 1, 2]`. The expected output should include unique permutations, but I’m getting duplicates in the result, such as `[1, 1, 2]` appearing multiple times. I've tried using a set to filter the results after generating them, but that feels like a workaround rather than a solution. Is there a better way to handle this case directly in the recursive logic? Also, how should I modify the backtracking approach to prevent duplicates without the need for post-processing the result? Any advice on best practices for this kind of recursive permutation generation would be greatly appreciated!