leetcode

Leetcode - Pascal's Triangle Solution

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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 in python

class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        triangle = [[1]]
        for _ in range(1,numRows):
            prev_row = triangle[-1]
            row = [1]
            for i in range(1,len(prev_row)):
                row.append(prev_row[i]+prev_row[i-1])
            row.append(1)
            triangle.append(row)
        return triangle

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