leetcode[46]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 perm(vector<int> &num, int i, int N, vector<vector<int>> &res)
{
if(i==N)
res.push_back(num);
for (int j=i;j<N;j++)
{
swap(num[i],num[j]);
perm(num,i+1,N,res);
swap(num[j],num[i]);
}
}
vector<vector<int> > permute(vector<int> &num)
{
vector<vector<int> > res;
perm(num,0,num.size(),res);
return res;
}
};