[leetcode]Pascal's Triangle

= =就是个模拟题

class Solution {
public:
    vector<vector<int> > generate(int numRows) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        vector<vector<int> > ans;
        vector<int> tmp;
        if(numRows == 0)  return ans;
        tmp.push_back(1); ans.push_back(tmp);
        for(int i = 1 ; i < numRows ; i++){
            int len = ans[i-1].size();
            tmp.clear();
            tmp.push_back(1);
            for(int j = 1 ; j < len ; j++)
            {
                int num = ans[i-1][j] + ans[i-1][j-1];
                tmp.push_back(num);
            }
            tmp.push_back(1);
            ans.push_back(tmp);
        }
        return ans;
    }
};