[LeetCode]-Palindrome Number 判断整数回文

SUN20082567

于 2014-08-17 15:38:58 发布

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本文介绍了一个用于检测整数是否为回文数的算法，避免使用额外的空间，并特别注意负数和整数溢出的情况。

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Palindrome Number

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

click to show spoilers.

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.

思路：获取integer的逆向值，用取余的办法。对于负数，直接判断不回文。对于整形逆转后溢出情况，考虑转换为unsigned int。

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0)return false;
        unsigned int b=0;
        unsigned int a=x;
        while(a){
            b*=10;
            b+=a%10;
            a=a/10;
        }
        if(b==x)return true;
        else
            return false;
    }
};