-
Notifications
You must be signed in to change notification settings - Fork 0
/
119PascalsTriangle2.swift
47 lines (43 loc) · 1.46 KB
/
119PascalsTriangle2.swift
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
/*
Given an integer rowIndex, return the rowIndexth (0-indexed) row of the Pascal's triangle.
In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:
Visualization - https://upload.wikimedia.org/wikipedia/commons/0/0d/PascalTriangleAnimated2.gif
Example 1:
Input: rowIndex = 3
Output: [1,3,3,1]
Example 2:
Input: rowIndex = 0
Output: [1]
*/
struct Solution {
static func getRow(_ rowIndex: Int) -> [Int] {
guard rowIndex > 0 else { return [1] }
guard rowIndex != 1 else { return [1, 1] }
var previousRow: [Int] = [1,1]
for index in 2...rowIndex {
let newRow = rowGenerator(previousRow: previousRow)
if index != rowIndex {
previousRow = newRow
} else {
return newRow
}
}
return [1]
}
static func rowGenerator(previousRow: [Int]) -> [Int] {
let newRowNumsCount = previousRow.count + 1
var numsArray: [Int] = []
for num in 1...newRowNumsCount {
let index = num - 1
if index == 0 || index == newRowNumsCount - 1 {
numsArray.append(1)
} else {
let rightPreviousRowValue = previousRow[index - 1]
let leftPreviousRowValue = previousRow[index]
let newValue = rightPreviousRowValue + leftPreviousRowValue
numsArray.append(newValue)
}
}
return numsArray
}
}