LeetCode 46: 全排列[C++][Go]

问题描述

给定一个没有重复数字的序列，返回其所有可能的全排列。

示例:

输入: [1,2,3]
输出:
[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

思路

dfs+递归：夹逼递归

C++

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<int> tmp;
        vector<vector<int>> ans;
        
        int len = nums.size();
        vector<bool> idx(len,0); //1代表该数进入排列，0相反
        
        dfs(ans,tmp,idx,nums,len);
        
        return ans;
        
    }
    
    
    void dfs(vector<vector<int>> &ans,vector<int> &tmp,vector<int> &idx,vector<int> &nums,int len)
    {
        if(tmp.size() == nums.size())
        {
            ans.push_back(tmp);
            return;
        }
        
        for(int i = 0; i < len;i++)
        {
            if(idx[i] == 1)continue;
            idx[i] = 1;
            tmp.push_back(nums[i]);
            dfs(ans,tmp,idx,nums,len);
            tmp.pop_back();
            idx[i] = 0;
        }
        
    }
    
};

Go

func permute(nums []int) [][]int {
    
    n := len(nums)
    tmp := make([]int,n)
    ans := make([][]int,0)
    idx := make([]bool,n)    //默认0
    dfs(&ans,idx,tmp,nums,n,0)
    return ans
}


func dfs(ans *[][]int,idx []bool,tmp []int,nums []int,n int,cur int) {
    
    if cur == n {
        t := make([]int,n)
        copy(t,tmp)			//必须copy出来，不然共享变量底层，答案会输出一样
        *ans = append(*ans,t)
        return
    }
    
    for i := 0;i < n;i++{
        if idx[i] == true{
            continue
        }
        
        idx[i] = true
        tmp[cur] = nums[i]
        dfs(ans,idx,tmp,nums,n,cur+1)
        idx[i] = false
    }
}