9.Palindrome Number

题目

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

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Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

解题思路

需要注意的有以下几点：

1.负数不是回文数；

2.不能将数转换成字符串，因为这需要额外的空间；

3.不能将数转置，因为可能溢出。

代码

    public boolean isPalindrome(int x){if(x<0)return false;int xx=x;int n=1;while(xx/10!=0){++n;xx/=10;}for(int i=0,j=n-1;j-i>=1;++i,--j){if((int)(x/Math.pow(10,i))%10 != (int)(x/Math.pow(10,j))%10)return false;}return true;}

运行结果