""" File: permutations_ii.py Created Time: 2023-04-15 Author: krahets (krahets@163.com) """ def backtrack( state: list[int], choices: list[int], selected: list[bool], res: list[list[int]] ): """回溯演算法:全排列 II""" # 當狀態長度等於元素數量時,記錄解 if len(state) == len(choices): res.append(list(state)) return # 走訪所有選擇 duplicated = set[int]() for i, choice in enumerate(choices): # 剪枝:不允許重複選擇元素 且 不允許重複選擇相等元素 if not selected[i] and choice not in duplicated: # 嘗試:做出選擇,更新狀態 duplicated.add(choice) # 記錄選擇過的元素值 selected[i] = True state.append(choice) # 進行下一輪選擇 backtrack(state, choices, selected, res) # 回退:撤銷選擇,恢復到之前的狀態 selected[i] = False state.pop() def permutations_ii(nums: list[int]) -> list[list[int]]: """全排列 II""" res = [] backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res) return res """Driver Code""" if __name__ == "__main__": nums = [1, 2, 2] res = permutations_ii(nums) print(f"輸入陣列 nums = {nums}") print(f"所有排列 res = {res}")