LeetCode 46 - Permutations

Permutations

Given a collection of distinct 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]

.

My Code

class Solution {
public:
void doPermute(vector<vector<int> >& res, vector<int> r, vector<int> v)
{
int size = v.size();
if (size == 1)
{
r.push_back(v[0]);
res.push_back(r);
return;
}

for (int i = 0; i < size; i++)
{
vector<int> rr(r);
vector<int> vv(v);
rr.push_back(v[i]);
vv.erase(vv.begin() + i);
doPermute(res, rr, vv);
}
}

vector<vector<int> > permute(vector<int>& nums) {
vector<vector<int> > res;
vector<int> r;
vector<int> v(nums);
doPermute(res, r, v);

return res;
}
};Runtime: 20 ms