Add palindrome number

Author: xiangzhai

palindrome/SConstruct

@@ -1,3 +1,5 @@
 env = Environment(CCFLAGS='-g')
 
 env.Program('palin_str.cpp')
+
+env.Program('palin_num.cpp')

palindrome/palin_num.cpp

@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+unsigned int reverse(unsigned int num) 
+{
+    unsigned int rev = 0;
+
+    while (num) 
+    {
+        rev = rev * 10 + num % 10;
+        num /= 10;
+    }
+
+    return rev;
+}
+
+bool isPalindrome(int x) 
+{
+  if (x < 0) return false;
+  int div = 1;
+  while (x / div >= 10) {
+    div *= 10;
+  }        
+  while (x != 0) {
+    int l = x / div;
+    int r = x % 10;
+    if (l != r) return false;
+    // remove l and r
+    // l -------------- r
+    x = (x % div) / 10;
+    // remove l and r 2 digits
+    div /= 100;
+  }
+  return true;
+}
+
+int main(int argc, char* argv[]) 
+{
+    unsigned int num = 616;
+
+    printf("%d\n", argv[1] ? reverse(atoi(argv[1])) : reverse(num));
+    
+    printf("%d\n", argv[1] ? isPalindrome(atoi(argv[1])) : isPalindrome(num));
+
+    return 0;
+}