Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.

Analyse：判断一个整数是否是回文数。注意负数都不是回文数。

 1 class Solution {

 2 public:

 3     bool isPalindrome(int x) {

 4         if(x < 0) return false;

 5         string s;

 6         while(x){

 7             char temp = x % 10 + '0';

 8             s += temp;

 9             x /= 10;

10         }

11         bool result = true;

12         for(int i = 0; i < s.length() / 2; i++){

13             if(s[i] != s[s.length() - 1 - i]) return false;

14         }

15         return true;

16     }

17 };

 或者：

 1 class Solution {

 2 public:

 3     bool isPalindrome(int x) {

 4         if(x < 0) return false;

 5         else if(x < 10) return true;

 6         else{

 7             int div = 1000000000;

 8             while(x / div == 0) div /= 10;

 9             bool result = true;

10             while(x){

11                 int left = x / div;

12                 int right = x % 10;

13                 if(left != right){

14                     result = false;

15                     break;

16                 }

17                 x = (x- left * div) / 10;

18                 div /= 100;

19             }

20             return result;

21         }

22     }

23 };

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