LeetCode-Permutations

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]

.

class Solution {
public:
void sub(vector<vector<int> > & ret,vector<int>& num,int index){
if(index==num.size()){
ret.push_back(num);
return ;
}
int temp;
for(int i=index;i<num.size();i++){
temp=num[i];
num[i]=num[index];
num[index]=temp;
sub(ret,num,index+1);
temp=num[i];
num[i]=num[index];
num[index]=temp;
}
}
vector<vector<int> > permute(vector<int> &num) {
// Note: The Solution object is instantiated only once and is reused by each test case.
vector<vector<int> >ret;
sub(ret,num,0);
return ret;
}
};

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