118. Pascal's Triangle
Given numRows, generate the first numRows of Pascal's triangle.
For example, given numRows = 5,
Return
[
[1],
[1,1],
[1,2,1],
[1,3,3,1],
[1,4,6,4,1]
]
@tag-array

Algorithm

The first and last number of each line is 1. Starting from the third line, each number in the middle is the sum of the left and right numbers of the previous line.