46. 全排列 @Python @Go

原题

https://leetcode.cn/problems/permutations/description/

思路

回溯法 + 集合

复杂度

时间：O(C(n, n))
空间：O(C(n, n))

Python代码

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        ans = []
        visited = set()

        def backtrack(path):
            if len(path) == len(nums):
                ans.append(path[:])
                return 
            for i in range(len(nums)):
                if nums[i] not in visited:
                    visited.add(nums[i])
                    path.append(nums[i])
                    backtrack(path)
                    # 还原
                    path.pop()
                    visited.remove(nums[i])
        
        backtrack([])
        return ans 

Go代码

func permute(nums []int) [][]int {
	var ans [][]int
	visited := map[int]bool{}
	// 匿名函数
	var backtrack func([]int)
	backtrack = func(path []int) {
		if len(path) == len(nums) {
			// 复制路径
			com := make([]int, len(path))
			copy(com, path)
			ans = append(ans, com)
			return
		}
		for i := 0; i < len(nums); i++ {
			if !visited[nums[i]] {
				visited[nums[i]] = true
				path = append(path, nums[i])
				backtrack(path)
				// 还原
				path = path[:len(path)-1]
				delete(visited, nums[i])
			}
		}
	}
	backtrack([]int{})
	return ans
}