【LeetCode】9. Palindrome Number - Java实现

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1. 题目描述：

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?

2. 思路分析：

题目的意思是判断一个数字是否是回文数字，要求不要转成字符串进行求解。
思路就是找出该数字的前一半和后一半的逆序，比较是否相等，如果相等返回true，否则返回false。
注意：数字有奇数位时的处理。

3. Java代码：

源代码：见我GiHub主页

代码：

public static boolean isPalindrome(int x) {
    if (x == 0) {
        return true;
    }

    if (x < 0 || x % 10 == 0) {
        return false;
    }

    int reverse = 0;
    while (x > reverse) {
        reverse = reverse * 10 + x % 10;
        x /= 10;
    }

    return x == reverse || x == reverse / 10;
}