LeetCode- Palindrome Number

作者：disappearedgod

文章出处：http://blog.youkuaiyun.com/disappearedgod/article/details/38776961

时间：2014-8-23

题目

Palindrome Number

  Total Accepted: 19059  Total Submissions: 65626 My Submissions

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.

解法

不能有额外的空间（不确定长度的堆空间）

转换成 如何找第一位和最末一位 && 比对后如何处理。

对于int来说 科学计数法：基数、每一位上的值、除法的余数和商

public class Solution {
    public boolean isPalindrome(int x) {
        if(x < 0)
            return false;
        if(x<10)
            return true;
        int base = 1;
        while( x / base >= 10 ){
            base *= 10;
        }

        while(x > 0){// if the length of x[] is odd, base of last cycle is 1
            if(x / base == x % 10){
                x -= base * (x / base);
                x /= 10;
                base /= 100;
            }
            else
                return false;
        }
        return true;
        
    }
}

结果

返回

LeetCode Solution(持续更新，java>c++)