LeetCode-46-全排列

输入: [1,2,3]
输出:
[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

class Solution {
    public List<List<Integer>> permute(int[] nums) {
        int len = nums.length;
        List<List<Integer>> res = new ArrayList<>();
        if(len==0) return res;
        boolean[] visited = new boolean[len];
        List<Integer> path = new ArrayList<>();
        dfs(nums,len,0,path,visited,res);
        return res;
    }

    public void dfs(int[] nums, int len, int depth,
                     List<Integer> path, boolean[] visited,
                     List<List<Integer>> res){
        if(len==depth){
            res.add(new ArrayList<>(path));
            return;
        }
        for(int i=0;i<len;i++){
            if(!visited[i]){
                path.add(nums[i]);
                visited[i] = true;
                dfs(nums,len,depth+1,path,visited,res);
                visited[i] = false;
                path.remove(path.size()-1);
            }
        }
    }
}