46. Permutations java solutions

Given a collection of distinct numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:

[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

Subscribe to see which companies asked this question

public class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> ans = new ArrayList<List<Integer>>();
        DFS(ans,0,nums);
        return ans;
    }
    
    public void DFS(List<List<Integer>> ans, int k, int[] nums){
        if(k == nums.length){
            List<Integer> list = new ArrayList<Integer>();
            for(int n : nums) list.add(n);
            ans.add(list);
        }
        
        for(int i = k; i< nums.length; i++){
            Swap(nums,k,i);
            DFS(ans,k+1,nums);
            Swap(nums,k,i);
        }
    }
    
    public void Swap(int[] num, int i, int j){
        int tmp = num[i];
        num[i] = num[j];
        num[j] = tmp;
    }
}

47. Permutations II java solutions

全排列就是从第一个数字起每个数分别与它后面的数字交换.

大神链接：

http://blog.csdn.net/happyaaaaaaaaaaa/article/details/51534048