LeetCode – Refresh – Palindrome Number

1. x/rec >= 10.

2. find start and end of a number.

 1 class Solution {
 2 public:
 3     bool isPalindrome(int x) {
 4         if (x < 0) return false;
 5         int rec = 1;
 6         while (x/rec >= 10) rec *= 10;
 7         while (x > 0) {
 8             int l = x/rec, r = x%10;
 9             if (l != r) return false;
10             x = x%rec/10;
11             rec /= 100;
12         }
13         return true;
14     }
15 };