118. Pascal's Triangle

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Difficulty: Easy 

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]]
Python Solution:

class Solution:
 def generate(self, numRows: int) -> List[List[int]]:
 l=[[1],[1,1]]
 if numRows==1:
 return [[1]]
 else:
 for _ in range(3,numRows+1):
 m=[1]
 for i in range(len(l[-1])-1):
 m.append(l[-1][i]+l[-1][i+1])
 m.append(1)
 l.append(m)
 return l

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