From d2ef0b367822c69e7acc43de09eafe0dac760eca Mon Sep 17 00:00:00 2001
From: zafar-hussain <zafar_hussain2000@hotmail.com>
Date: Thu, 8 Oct 2020 20:37:18 +0500
Subject: [PATCH] Adding solution for issue #36  'Check Palindrome of integers'

---
 problems/palindrome/isPalindrome?.rkt | 39 +++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 problems/palindrome/isPalindrome?.rkt

diff --git a/problems/palindrome/isPalindrome?.rkt b/problems/palindrome/isPalindrome?.rkt
new file mode 100644
index 00000000..1c050467
--- /dev/null
+++ b/problems/palindrome/isPalindrome?.rkt
@@ -0,0 +1,39 @@
+#lang racket
+ 
+;Build a function that checks weather a given number is a palindrome or not without using a strings. Implement it using any language.
+;
+;For example:
+;input: 12321
+;output: true
+;
+; input: 12344321
+; output: True
+
+;; intution
+;; n and reverse n will be same for a palindrome
+;; will use reverse-number (see pr #341 for issue #35)
+
+;; I got the Idea from link below
+;; https://www.integers.co/questions-answers/is-12344321-a-palindrome-number.html
+
+
+
+;; code
+(define (isPalinDrome n)
+  (local [
+          (define (reverse-n n acc)                               ; using an decerasing accumulator
+            (cond [(= (order-of-magnitude n) 0) n]                ; basecase, used to stop recursion
+                  [else
+                   (+ 
+                    (* (modulo n 10) (expt 10 acc))               ; get the right-most digit of n, multiply it with 10^x
+                    (reverse-n (quotient n 10) (sub1 acc)))]))
+
+          (define (reverse-number num)
+            (reverse-n num (order-of-magnitude num)))
+          ]
+    (= (reverse-number n) n)))
+
+; test examples
+;(equal? (isPalinDrome 9) true) 
+;(equal? (isPalinDrome 12349321) false)
+;(equal? (isPalinDrome 12321) true)