Problem 9: palindrome number

problems/9-palindrome-number/Makefile

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+../template/Makefile

problems/9-palindrome-number/lib.c

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+#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

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+#pragma once
+#include <stdbool.h>
+
+bool isPalindrome(int x);

problems/9-palindrome-number/main.c

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+#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;
+}