LeetCode_Permutations

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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]

　　找全排列，ＤＦＳ的一般应用

class Solution {
public:
   void DFS(vector<int> &num, int size,vector<int> temp)
    {
        if(size == n){
            result.push_back(temp);
            return ;
        }
        for(int i = 0; i< n; i++)
        {
           if(flag[i] == false)
           {
                temp[size] = num[i];
                flag[i] = true;
                DFS(num, size+1, temp);
                flag[i] = false;
           }
        }
    }
    vector<vector<int> > permute(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        n = num.size();
        result.clear();
        flag.resize(n,false);
        
        if(n == 0) return result;
        vector<int> temp(n,0) ;         
        DFS(num,0,temp);   
        
        return result ;
    }
private :
   int  n;
   vector<bool> flag;
   vector<vector<int>> result;   
};