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;    }};