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

Question

Can anyone tell me what\'s wrong with the code. Find the largest palindrome made from the product of two 3-digit numbers.

function largestPalind         


        

Answer 1

Swift 3:

// my approach is to make 6-digit palindrome first and then 
// check if I can divide it by 3-digit number 
// (you can see some visual listing at the end of the code)
// execution time on my laptop is around: 2.75409698486328 sec

import Foundation

func maxPalindrom() -> Int {

    var result = 999999
    var i = 9
    var j = 9
    var k = 9

    while true {
        while true {
            while true {
                print("in K loop: \(result) k = \(k)")

                if isDivisible(number: result) {
                    return result
                }
                if k <= 0 {
                    k = 9
                    result += 9900
                    break
                }
                result -= 1100
                k -= 1
            }

            print("in J loop: \(result)")
            if isDivisible(number: result) {
                return result
            }
            if j < 0 {
                j = 9
                result += 90090
                break
            }
            result -= 10010
            j -= 1
        }

        print("in I loop: \(result)")
        if isDivisible(number: result) {
            return result
        }
        if i < 0 {
            break
        }
        result -= 100001
        i -= 1
    }

    if result == 100001 {
        return -1
    }

    return -1
}


func isDivisible(number: Int) -> Bool {
    var i = 999

    while true {

        if number % i == 0 && number / i < 999 {
            return true
        }

        if i < 500 {
            return false
        }

        i -= 1
    }

}


let start = NSDate()
print(maxPalindrom())       // 906609
let end = NSDate()

print("executio time: \(end.timeIntervalSince(start as Date)) sec") // ~ execution time: 2.75409698486328 sec

//in K loop: 999999 k = 9
//in K loop: 998899 k = 8
//in K loop: 997799 k = 7
//in K loop: 996699 k = 6
//in K loop: 995599 k = 5
//in K loop: 994499 k = 4
//in K loop: 993399 k = 3
//in K loop: 992299 k = 2
//in K loop: 991199 k = 1
//in K loop: 990099 k = 0
//in J loop: 999999
//in K loop: 989989 k = 9
//in K loop: 988889 k = 8
//in K loop: 987789 k = 7
//in K loop: 986689 k = 6
//in K loop: 985589 k = 5
//in K loop: 984489 k = 4
//in K loop: 983389 k = 3
.....