diff --git a/Project-Euler/Problem4.js b/Project-Euler/Problem4.js
index bcc4d880b6..1ae3ef197b 100644
--- a/Project-Euler/Problem4.js
+++ b/Project-Euler/Problem4.js
@@ -1,46 +1,30 @@
-// https://projecteuler.net/problem=4
-/* 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.
-*/
-const largestPalindromic = (digits) => {
- let i
- let n
- let m
- let d
- let limit
- let number = 0
+function isPalindrome (number) {
+ // just 2 random names for variables!
+ const look = String(number)
+ let hear = false
- for (i = 1; i < digits; i++) { - number = 10 * number + 9 - } - const inf = number // highest (digits - 1) number, in this example highest 2 digit number - const sup = 10 * number + 9 // highest (digits) number, in this example highest 3 digit number - - const isPalindromic = (n) => {
- let p = 0
- const q = n
- let r
- while (n> 0) {
- r = n % 10
- p = 10 * p + r
- n = Math.floor(n / 10)
+ for (let i = 0; i < look.length; i++) { + if (look[i] === look[(look.length) - (i + 1)]) { + hear = true + } else { + return false } - return p === q // returning whether the number is palindromic or not } + return hear +} + +function largestPalindromeProduct (n) { + let product = 0 + let largestPalindrome = 11 - for (n = sup * sup, m = inf * inf; n> m; n--) {
- if (isPalindromic(n)) {
- limit = Math.ceil(Math.sqrt(n))
- d = sup
- while (d>= limit) {
- if (n % d === 0 && n / d> inf) {
- return n
- }
- d -= 1
- }
+ for (let i = 10 ** (n - 1); i < 10 ** n; i++) { + for (let j = 10 ** (n - 1); j < 10 ** n; j++) { + product = i * j + if (isPalindrome(product) && product> largestPalindrome) { largestPalindrome = product }
}
}
- return NaN // returning not a number, if any such case arise
+ return largestPalindrome
}
-console.log(largestPalindromic(3))
+console.log(isPalindrome(9009))
+console.log(largestPalindromeProduct(2))