118 Pascal's Triangle

class Solution {
public:
vector<vector<int>> generate(int numRows) {
vector<vector<int>> res;
vector<int> tmp;
vector<int> tmp1;
int i=1;
while(i<=numRows)
{
tmp1.clear();
tmp1.push_back(1);
for(int j=0;j<i-2;++j)
tmp1.push_back(tmp[j]+tmp[j+1]);
if(i!=1)
tmp1.push_back(1);
++i;
tmp = tmp1;
res.push_back(tmp);
}
return res;
}
};