leetcode-9-palindrome-number 回文数

题目

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.

Follow up:

Coud you solve it without converting the integer to a string?

分析

这是一道比较简单的题目
只要分析出来三个判断就可以

1. 等于零
2. 小于零
3. 大于零

   等于零

   等于零肯定成立，因为零无论正着念，倒着读都是零

   小于零

   有题目知等于零的时候不成立

   大于零

   这是相对来说比较复杂的地方了，设置参数将x倒置比较即可

   bool isPalindrome(int x) {
        if(x==0)
       {
           return true;
       }
           else if(x<0)
       {
           return false;
       }
           else
       {
           int x1=x;
           int y=0;
           int tmp=0;
           while(x1!=0)
           {
               tmp=x1%10;
               x1=x1/10;
               y=y*10+tmp;
           }
           if(x==y)
           {
               return true;
           }
           else
           {
               return false;
           }
   
       }
   
           
   }