class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        rows = []
        for i in range(1, numRows + 1):
            row = [1 if j == 0 or j >= i - 1 else rows[i-2][j-1]+rows[i-2][j] for j in range(i)]
            rows.append(row)
        return rows