帕斯卡三角形—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]
]
Pascal’s Triangle
第一个元素和最后一个元素赋值为 1
中间的每个元素，等于上一行的左上角和右上角元素之和

vector<vector<int>> generate(int numRows) {
    vector<vector<int>> result;

    for (int i = 0; i < numRows; ++i)
    {
        result.emplace_back(i + 1);
        result[i][0] = 1;
        result[i][i] = 1;
        for (int j = 1; j < i; ++j)
            result[i][j] = result[i - 1][j - 1] + result[i - 1][j];
    }

    return result;
}