Pascal's Triangle

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]
]

模拟由金子塔型换成下三角型会看的清楚一些，注意numRows = 1,2的特殊情况。总体来说简单。

class Solution {
public:
    vector<vector<int> > generate(int numRows) {
        vector<vector<int> > re;
        
        for(int i = 1 ; i <= numRows ; i++)
        {
            vector<int> vec;
            vec.push_back(1);
            int j;
            if(i == 1){
                re.push_back(vec);
                continue;
            }
            if(i == 2){
                vec.push_back(1);
                re.push_back(vec);
                continue;
            }
            for(j = 1 ; j < i-1; j++)vec.push_back(re[i-2][j-1]+re[i-2][j]);
            vec.push_back(1);
            re.push_back(vec);
            
        }
        return re;
    }
};