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]
]

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