Leetcode 118 Pascal's Triangle 数论递推

杨辉三角，即组合数 递推

 class Solution {
     vector<vector<int>> v;
     public:
     Solution() {
         for(int i = ; i < ; ++i){
             vector<int> t(i+,);
             for(int j = ; j < i; ++j){
                 t[j] = v[i-][j] + v[i-][j - ];
             }
             v.push_back(t);
         }
     }

     vector<vector<int>> generate(int numRows) {
         return vector<vector<int>>(v.begin(), v.begin() + numRows);
     }
 };