78. 子集 @Python @Go

原题

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

思路

回溯法

复杂度

时间：O(n!)
空间：O(n!)

Python代码

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

        def backtrack(k, start, path):
            if len(path) == k:
                ans.append(path.copy())
                return 
            for i in range(start, len(nums)):
                path.append(nums[i])
                backtrack(k, i+1, path)
                # 还原
                path.pop()

        for k in range(len(nums) + 1):
            backtrack(k, 0, [])
        return ans 
        

Go代码

func subsets(nums []int) [][]int {
	var ans [][]int
	// 匿名函数
	var backtrack func(int, int, []int)
	backtrack = func(k int, start int, path []int) {
		if len(path) == k {
			com := make([]int, len(path))
			copy(com, path)
			ans = append(ans, com)
			return
		}
		for i := start; i < len(nums); i++ {
			path = append(path, nums[i])
			backtrack(k, i+1, path)
			// 还原
			path = path[:len(path)-1]
		}
	}

	for k := 0; k <= len(nums); k++ {
		backtrack(k, 0, []int{})
	}
	return ans
}