The challenge
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
The solution in Python code
class Solution:
def generate(self, numRows: int) -> List[List[int]]:
triangle = [[1]]
for j in range(1, numRows):
prev = triangle[-1]
triangle.append([1] + [prev[i]+prev[i+1] for i in range(len(prev)-1)] + [1])
return triangle
