118. 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>> pascal_triangle(numRows);

        if (numRows == 0)
        {
            return pascal_triangle;
        }
    
        for (int i = 0; i < numRows; ++i)
        {
            pascal_triangle[i].push_back(1);

            for (int j = 1; j < i; ++j)
            {
                pascal_triangle[i].push_back(pascal_triangle[i-1][j-1] + pascal_triangle[i-1][j]);
            }

            if (i != 0)
            {
                pascal_triangle[i].push_back(1);
            }
        }

        return pascal_triangle;
    }
};