class Solution {public:    vector<vector<int> > generate(int numRows) {        int i,j;        if(numRows==0)        {            return vector<vector<int> >();        }        vector<vector<int> > vec1;         vector<int> vec2;        vec2.push_back(1);        vec1.push_back(vec2);        for(i=1;i<numRows;i++)        {            vec2.clear();            vec2.push_back(1);            for(j=1;j<i;j++)            {                vec2.push_back(vec1[i-1][j]+vec1[i-1][j-1]);            }            vec2.push_back(1);            vec1.push_back(vec2);        }        return vec1;    }};