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>> res;
        if(numRows == 0)
            return res;
        vector<int> temp(1,1);
        res.push_back(temp);
        for(int i=1; i<numRows; i++)
        {
            temp.clear();
            temp.push_back(1);
            for(int j=1; j<i; j++)
                temp.push_back(res[i-1][j-1]+res[i-1][j]);
            temp.push_back(1);
            res.push_back(temp);
        }
        return res;
    }
};

LeetCode--Pascal's Triangle