118-pascals-triangle

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Description

Given an integer numRows, return the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

 

Example 1:

Input: numRows = 5
Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]

Example 2:

Input: numRows = 1
Output: [[1]]

 

Constraints:

• 1 <= numRows <= 30

Solution(Python)

class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        dp = [[1 for j in range(i + 1)] for i in range(numRows)]

        for i in range(2, numRows):
            for j in range(1, i):
                dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1]
        return dp