Leetcode_46 全排列

题目描述

题解

java

java里面不可以在方法里面定义全局变量

import java.util.*;
public class Leetcode_46 {

    boolean[] isUsed = new boolean[10000];

    public List<List<Integer>> permute(int[] nums) {



        List<List<Integer>> ret = new ArrayList<>();
        if(nums.length==0)
            return ret;
        ArrayList<Integer> p = new ArrayList<>();
        findPermute(nums,0,p,ret);
        return ret;

    }


    private void findPermute(int[] nums, int offset, ArrayList<Integer> p,List<List<Integer>> ret)
    {

        if(offset>=nums.length)
        {
            ret.add(new ArrayList<Integer>(p));
            return;
        }

        for(int i = 0; i<nums.length; i++)
        {
            if(!isUsed[i])
            {
                isUsed[i] = true;
                p.add(nums[i]);
                System.out.println(p.toString());

                findPermute(nums,offset+1,p,ret);
                p.remove(p.size()-1);
                isUsed[i] = false;
            }
        }
    }

    public static void main(String[] args)
    {
        Leetcode_46 a = new Leetcode_46();
        int[] nums = {1,2,3};
        List<List<Integer>> ret = a.permute(nums);
        System.out.println(ret.toString());

    }

}

c++

class Solution {
private:
    vector<vector<int>> res;
    vector<bool> used;
    void generatePermutation(const vector<int>& nums, int index, vector<int>& p)
    {
        if(index == nums.size())
        {
            res.push_back(p);
            return;
        }
        for(int i = 0; i<nums.size();i++)
        {
            if(!used[i]){
                used[i] = true;
                p.push_back(nums[i]);
                generatePermutation(nums,index+1,p);
                p.pop_back();
                used[i] = false;       

            }

        }
        return;

    }
public:
    vector<vector<int>> permute(vector<int>& nums) {
        res.clear();
        if(nums.size()==0)
            return res;
        used = vector<bool>(nums.size(), false);
        vector<int> p;
        generatePermutation(nums,0,p);
        return res;

    }
};