Palindrome Number——LeetCode进阶路⑨

//原题链接https://leetcode.com/problems/palindrome-number/

• 题目描述

  Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

  Example 1:

  Input: 121
  Output: true
  

  Example 2:

  Input: -121
  Output: false
  Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
  

  Example 3:

  Input: 10
  Output: false
  Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
  

• 思路分析
  1.空间复杂度为O(1)
  2.负数都不是回文数，返回false
  3.利用消消乐想法，末位与首位相同抵消，相异直接返回false
• 源码附录

  class Solution {
      public boolean isPalindrome(int x) {
          if(x<0){
              return false;
          }
          
          else{
              
              long temp = 1;
              while(temp <= x/10){
                      temp = temp *10 ;
                  }
              
              while(x>0){
                  if(x%10 != x/temp){
                      return false;
                  }
                  x = (x % (int)temp)/10;
                  temp = temp / 100;
              }
          return true;
          }
      }
  }