Permutations

来源：互联网发布：sql修改字段数据类型编辑：程序博客网时间：2024/05/18 03:15

问题描述

Given a collection of 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], and [3,2,1].

思考：递归求解

想法

1、设number为存放未被加入序列的List，curNum为已加入序列的list
2、逐个将number中的元素加入cueNum，递归，如果number长度为0，则
将curNum中的内容加入result，

代码

public class Solution {    public List<List<Integer>> permute(int[] num) {        List<List<Integer>> result = new LinkedList<List<Integer>>();        if(num.length == 0)            return result;        List<Integer> number = new LinkedList<>();        List<Integer> curNum = new LinkedList<>();        for(int i = 0; i < num.length; i++)            number.add(num[i]);        recurPermutation(number, curNum, result);        return result;     }    private void recurPermutation(List<Integer> number, List<Integer> curNum, List<List<Integer>> result){        if(number.size() == 0){            result.add(new LinkedList<Integer>(curNum));            return;        }        for(int i = 0; i < number.size(); i++){            int temp = number.remove(i);            curNum.add(temp);            recurPermutation(number,curNum,result);            curNum.remove(curNum.size() - 1);            number.add(i,temp);        }    }}

0 0