[leetcode] 9. Palindrome Number

原题:

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?

思路:

如有负号直接返回false,其余对x进行反转,对比原答案与反转结果.

c++代码实现:

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0) 
            return false;
        long res=0, z=x;
        while(z)
        {
            res= res*10+z%10;
            z/=10;
        }
        return res==x;
    }
};