Problem 9: ruby rewrite

problems/9-palindrome-number/Makefile

@@ -1 +0,0 @@
-../template/Makefile

problems/9-palindrome-number/lib.c

@@ -1,32 +0,0 @@
-#include "lib.h"
-
-bool isPalindrome(int x) {
-    if (x < 0)
-        return false;
-
-    // Find length and calculate divisor
-    int len = 0;
-    int div = 1;
-    int copy = x;
-    while (copy > 0) {
-        copy /= 10;
-        if (len != 0)
-            div *= 10;
-        len++;
-    }
-
-    // Compare digits
-    for (int i=0; i<len/2; i++) {
-        int a = x / div;
-        int b = x % 10;
-        if (a != b)
-            return false;
-        
-        // Remove first and last digit
-        x = x % div;
-        x /= 10;
-        div /= 100;
-    }
-
-    return true;
-}

problems/9-palindrome-number/lib.h

@@ -1,4 +0,0 @@
-#pragma once
-#include <stdbool.h>
-
-bool isPalindrome(int x);

problems/9-palindrome-number/main.c

@@ -1,18 +0,0 @@
-#include <stdio.h>
-#include "lib.h"
-
-int main() {
-    int a = 121;
-    printf("Test 1: %d\n", isPalindrome(a) == 1);
-
-    int b = -121;
-    printf("Test 2: %d\n", isPalindrome(b) == 0);
-
-    int c = 1234554321;
-    printf("Test 3: %d\n", isPalindrome(c) == 1);
-
-    int d = 2147483647;
-    printf("Test 4: %d\n", isPalindrome(d) == 0);
-
-    return 0;
-}

problems/9-palindrome-number/main.rb

@@ -0,0 +1,15 @@
+# @param {Integer} x
+# @return {Boolean}
+def is_palindrome(x)
+  return false if x.negative?
+
+  copy = x
+  inv = 0
+
+  while copy.positive?
+    inv = inv * 10 + copy % 10
+    copy /= 10
+  end
+
+  inv == x
+end

problems/9-palindrome-number/test.rb

@@ -0,0 +1,16 @@
+require_relative 'main'
+require 'test/unit'
+
+class TestIsPalindrome < Test::Unit::TestCase
+  def test_palindrome
+    assert_equal(true, is_palindrome(121))
+  end
+
+  def test_negative
+    assert_equal(false, is_palindrome(-121))
+  end
+
+  def test_regular_number
+    assert_equal(false, is_palindrome(10))
+  end
+end