leetcode-009-Palindrome Number

P009 Palindrome Number

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

思路分析

• 负数==>false
• 从两头对数字逐渐切割，一旦有不同的==>false

代码

java

public class Solution009 {    public boolean isPalindrome(int x) {        if (x < 0)            return false;        else if (x <= 9)            return true;        int base = 1;        // 取得最高位的级数base=power(10,n)        while (x / base >= 10)            base *= 10;        while (x != 0) {            int left = x / base;            int right = x % 10;            if (left != right)                return false;            x -= base * left;// 去掉最高位            x /= 10;// 去掉最低位            base /= 100;// 去掉了两位数,base/100        }        return true;    }}

python

class Solution009(object):    def isPalindrome(self, x):        """        :type x: int        :rtype: bool        """        if x < 0:return False        elif x <= 9 :return True        base = 1        while x / base >= 10:            base *= 10        while x != 0:            l = x / base            r = x % 10            if l != r:return False            x -= l * base            x /= 10            base /= 100        return True