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Pascal Triangle ​

Problem Description ​

Given an integer A, equal to numRows, generate the first numRows of Pascal's triangle.

Pascal's triangle: To generate A[C] in row R, sum up A'[C] and A'[C-1] from the previous row R - 1.

Problem Constraints

0 <= A <= 25

Input Format

The first argument is an integer A, equal to the numRows.

Output Format

Return an array of array of integers, equal to pascal triangle.

Example Input

A = 5

Example Output

[
     [1],
     [1,1],
     [1,2,1],
     [1,3,3,1],
     [1,4,6,4,1]
]

Solution ​

swift
import Foundation

class Solution {
	func solve(_ A: inout Int) -> [[Int]] {
		var B = [[Int]]()
		if A == 0 {
			return B
		}
		B.append([1])
		if A == 1 {
			return B
		}
		for i in 2...A {
			var C = [Int](repeating:1,count:i)
			var last = B.last!
			for j in 1..<(i-1) {
				C[j] = last[j-1] + last[j]
			}
			B.append(C)
		}
		return B	
	}
}

References ​