【LeetCode】9. Palindrome Number

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.

判断一个整数是否是回文数。回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。

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?

你能不将整数转为字符串来解决这个问题吗？

2.Solutions

public static boolean isPalindrome(int x) {
    if(x < 0) return false;
    int y = x;
    int res = 0;
    while(y != 0) {
        res = res * 10 + y % 10;
        y /= 10;
    }
    return x == res;
}

Scala版

object Solution {
    def isPalindrome(x: Int): Boolean = {
        if(x < 0)
          return false
        var y = x
        var result = 0
        while(y != 0){
          result = result * 10 + y%10
          y /= 10
        }
        result == x
    }
}

（完）