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Algorithm

9. Palindrome Number

Description

Given an integer x, return true if x is a palindrome, and false otherwise.

Example 1:

Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.

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.

Constraints:

  • -231 <= x <= 231 - 1

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

Solution

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

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