A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 ×ばつ 99.

Find the largest palindrome made from the product of two 3-digit numbers.

What I've so far learned about Swift is that while the Playground is very cool for tinkering around, it definitely does not like big loops. So this time, I coded parts in the playground, but moved it over to an actual executable project to run the final code.

I'm interested in knowing any Swift tricks I missed. I did implement a new trick I learned in this solution, the stride feature.

import Foundation
func printTimeElapsedWhenRunningCode(title:String, operation:()->()) {
 let startTime = CFAbsoluteTimeGetCurrent()
 operation()
 let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
 println("Time elapsed for \(title): \(timeElapsed) s")
}
extension Int {
 func isPalindrome() -> Bool {
 return self == self.reversed()
 }
 
 func reversed() -> Int {
 var original: Int = self
 var reversed: Int = 0
 
 while original > 0 {
 reversed *= 10
 reversed += original % 10
 original /= 10
 }
 
 return reversed
 }
}
func largestPalindrome() {
 var left: Int = 999
 var right: Int = 999
 var largestPalindrome: Int = 0
 for left in stride(from: 999, through: 100, by: -1) {
 for right in stride(from: left, through: 100, by: -1) {
 let product: Int = left * right
 if product > largestPalindrome && product.isPalindrome() {
 largestPalindrome = product
 }
 }
 }
 println(String(largestPalindrome))
}
printTimeElapsedWhenRunningCode("Largest Palindrome", largestPalindrome)

The printTimeElapsedWhenRunningCode function is borrowed from Brad Larson's answer here, and on my computer, it says the code is running in about 0.27 to 0.28 seconds.

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 ×ばつ 99.

Find the largest palindrome made from the product of two 3-digit numbers.

What I've so far learned about Swift is that while the Playground is very cool for tinkering around, it definitely does not like big loops. So this time, I coded parts in the playground, but moved it over to an actual executable project to run the final code.

I'm interested in knowing any Swift tricks I missed. I did implement a new trick I learned in this solution, the stride feature.

import Foundation
func printTimeElapsedWhenRunningCode(title:String, operation:()->()) {
 let startTime = CFAbsoluteTimeGetCurrent()
 operation()
 let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
 println("Time elapsed for \(title): \(timeElapsed) s")
}
extension Int {
 func isPalindrome() -> Bool {
 return self == self.reversed()
 }
 
 func reversed() -> Int {
 var original: Int = self
 var reversed: Int = 0
 
 while original > 0 {
 reversed *= 10
 reversed += original % 10
 original /= 10
 }
 
 return reversed
 }
}
func largestPalindrome() {
 var left: Int = 999
 var right: Int = 999
 var largestPalindrome: Int = 0
 for left in stride(from: 999, through: 100, by: -1) {
 for right in stride(from: left, through: 100, by: -1) {
 let product: Int = left * right
 if product > largestPalindrome && product.isPalindrome() {
 largestPalindrome = product
 }
 }
 }
 println(String(largestPalindrome))
}
printTimeElapsedWhenRunningCode("Largest Palindrome", largestPalindrome)

The printTimeElapsedWhenRunningCode function is borrowed from Brad Larson's answer here, and on my computer, it says the code is running in about 0.27 to 0.28 seconds.

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 ×ばつ 99.

Find the largest palindrome made from the product of two 3-digit numbers.

What I've so far learned about Swift is that while the Playground is very cool for tinkering around, it definitely does not like big loops. So this time, I coded parts in the playground, but moved it over to an actual executable project to run the final code.

I'm interested in knowing any Swift tricks I missed. I did implement a new trick I learned in this solution, the stride feature.

Anyway, here's the code:

import Foundation
func printTimeElapsedWhenRunningCode(title:String, operation:()->()) {
 let startTime = CFAbsoluteTimeGetCurrent()
 operation()
 let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
 println("Time elapsed for \(title): \(timeElapsed) s")
}
extension Int {
 func isPalindrome() -> Bool {
 return self == self.reversed()
 }
 
 func reversed() -> Int {
 var original: Int = self
 var reversed: Int = 0
 
 while original > 0 {
 reversed *= 10
 reversed += original % 10
 original /= 10
 }
 
 return reversed
 }
}
func largestPalindrome() {
 var left: Int = 999
 var right: Int = 999
 var largestPalindrome: Int = 0
 for left in stride(from: 999, through: 100, by: -1) {
 for right in stride(from: left, through: 100, by: -1) {
 let product: Int = left * right
 if product > largestPalindrome && product.isPalindrome() {
 largestPalindrome = product
 }
 }
 }
 println(String(largestPalindrome))
}
printTimeElapsedWhenRunningCode("Largest Palindrome", largestPalindrome)

The printTimeElapsedWhenRunningCode function is borrowed from Brad Larson's answer here, and on my computer, it says the code is running in about 0.27 to 0.28 seconds.

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 ×ばつ 99.

Find the largest palindrome made from the product of two 3-digit numbers.

What I've so far learned about Swift is that while the Playground is very cool for tinkering around, it definitely does not like big loops. So this time, I coded parts in the playground, but moved it over to an actual executable project to run the final code.

I'm interested in knowing any Swift tricks I missed. I did implement a new trick I learned in this solution, the stride feature.

import Foundation
func printTimeElapsedWhenRunningCode(title:String, operation:()->()) {
 let startTime = CFAbsoluteTimeGetCurrent()
 operation()
 let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
 println("Time elapsed for \(title): \(timeElapsed) s")
}
extension Int {
 func isPalindrome() -> Bool {
 return self == self.reversed()
 }
 
 func reversed() -> Int {
 var original: Int = self
 var reversed: Int = 0
 
 while original > 0 {
 reversed *= 10
 reversed += original % 10
 original /= 10
 }
 
 return reversed
 }
}
func largestPalindrome() {
 var left: Int = 999
 var right: Int = 999
 var largestPalindrome: Int = 0
 for left in stride(from: 999, through: 100, by: -1) {
 for right in stride(from: left, through: 100, by: -1) {
 let product: Int = left * right
 if product > largestPalindrome && product.isPalindrome() {
 largestPalindrome = product
 }
 }
 }
 println(String(largestPalindrome))
}
printTimeElapsedWhenRunningCode("Largest Palindrome", largestPalindrome)

The printTimeElapsedWhenRunningCode function is borrowed from Brad Larson's answer here, and on my computer, it says the code is running in about 0.27 to 0.28 seconds.