Pascal's Triangle I

来源：Leetcode

原帖：https://oj.leetcode.com/problems/pascals-triangle/

题目：
Given numRows, generate the first numRows of Pascal's triangle.
For example, given numRows = 5,
Return
 [
      [1],
     [1,1]
    [1,2,1],
   [1,3,3,1],
  [1,4,6,4,1]
 ]

代码：

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