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permutations.py
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permutations.py
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"""
46. 全排列
数组 回溯
中等
给定一个不含重复数字的数组 nums ,返回其 所有可能的全排列 。你可以 按任意顺序 返回答案。
示例 1:
输入:nums = [1,2,3]
输出:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
示例 2:
输入:nums = [0,1]
输出:[[0,1],[1,0]]
示例 3:
输入:nums = [1]
输出:[[1]]
提示:
1 <= nums.length <= 6
-10 <= nums[i] <= 10
nums 中的所有整数 互不相同
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/permutations
"""
from typing import List
class Solution:
def permute(self, nums: List[int]) -> List[List[int]]:
def backtrack(first: int = 0):
if first >= n - 1:
res.append(nums[:])
return
for i in range(first, n):
nums[first], nums[i] = nums[i], nums[first]
backtrack(first + 1)
nums[first], nums[i] = nums[i], nums[first]
n = len(nums)
res = []
backtrack()
return res
if __name__ == '__main__':
solution = Solution()
result = solution.permute([1, 2, 3])
print(result)
assert set((tuple(i) for i in result)) == set(
(tuple(i) for i in [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]))
result = solution.permute([0, 1])
print(result)
assert set((tuple(i) for i in result)) == set(
(tuple(i) for i in [[0, 1], [1, 0]]))
result = solution.permute([1])
print(result)
assert set((tuple(i) for i in result)) == set(
(tuple(i) for i in [[1]]))