README_EN.md

9. Palindrome Number

中文文档

Description

Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

 

Example 1:

Input: x = 121
Output: true

Example 2:

Input: x = -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: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Example 4:

Input: x = -101
Output: false

 

Constraints:

• -231 <= x <= 231 - 1

 

Follow up: Could you solve it without converting the integer to a string?

Solutions

Python3

class Solution:
    def isPalindrome(self, x: int) -> bool:
        if x < 0:
            return False
        y, t = 0, x
        while t:
            y = y * 10 + t % 10
            t //= 10
        return x == y

Java

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

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