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45 lines
1.2 KiB
Python
45 lines
1.2 KiB
Python
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"""
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File: permutations_i.py
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Created Time: 2023-04-15
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Author: krahets (krahets@163.com)
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"""
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def backtrack(
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state: list[int], choices: list[int], selected: list[bool], res: list[list[int]]
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):
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"""回溯演算法：全排列 I"""
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# 當狀態長度等於元素數量時，記錄解
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if len(state) == len(choices):
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res.append(list(state))
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return
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# 走訪所有選擇
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for i, choice in enumerate(choices):
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# 剪枝：不允許重複選擇元素
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if not selected[i]:
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# 嘗試：做出選擇，更新狀態
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selected[i] = True
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state.append(choice)
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# 進行下一輪選擇
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backtrack(state, choices, selected, res)
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# 回退：撤銷選擇，恢復到之前的狀態
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selected[i] = False
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state.pop()
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def permutations_i(nums: list[int]) -> list[list[int]]:
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"""全排列 I"""
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res = []
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backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
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return res
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"""Driver Code"""
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if __name__ == "__main__":
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nums = [1, 2, 3]
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res = permutations_i(nums)
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print(f"輸入陣列 nums = {nums}")
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print(f"所有排列 res = {res}")
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