https://leetcode.com/problems/permutations/

Permutations.java

//https://leetcode.com/problems/permutations/
/**
 * 深度优先搜索框架
 */
public class Solution {
    public static List<List<Integer>> ans = new ArrayList<List<Integer>>();
    
    public static int[] path = new int[100];
    
    public static boolean[] v = new boolean[100];
    
    public static void robot(int idx, int[] nums){
        int n = nums.length;
        if(idx >= n){
            //record ans
            List<Integer> tmp = new ArrayList<Integer>();
            for(int i = 0 ; i < n ; i++){
                tmp.add(nums[path[i]]);
            }
            ans.add(tmp);
            return;
        }
        for(int i = 0 ; i < n ; i++){
            if(!v[i]){
                path[idx] = i;
                v[i] = true;
                robot(idx + 1, nums);
                v[i] = false;
            }
        }
    }
    
    public List<List<Integer>> permute(int[] nums) {
        ans.clear();
        robot(0, nums);
        return ans;
    }
}