LeetCode-46:Permutations

原题描述如下:

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]]

题意：给定一个数字，求1到n的全排列

解题思路：

Java代码：

public class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> resList = new ArrayList<List<Integer>>();
        List<Integer> list = new ArrayList<Integer>();
        
        for(int i=0; i<nums.length; ++i){
            list.add(nums[i]);
        }
        
        resList.add(list);
        
        getRes(resList, 0, nums.length);
        
        return resList;
    }
    

    public static void getRes(List<List<Integer>> resList, int k, int n){
        if(k != n){
            int size = resList.size();
            for(int i=0; i<size; ++i){
                List<Integer> list = resList.get(i);
                for(int j=k+1; j<n; ++j){
                    List<Integer> templist = new ArrayList<Integer>(list);
                    int k1 = templist.get(k);
                    templist.set(k, templist.get(j));
                    templist.set(j, k1);
                    resList.add(templist);
                }
            }
            
            getRes(resList, k+1, n);
        }
    }
}