9. Palindrome Number (Easy)

https://leetcode.com/problems/palindrome-number/

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?

Hints

Solutions

  • Java
class Solution {
    public boolean isPalindrome(int x) {
        if (x == 0) return true;
        if (x < 0) return false;

        int xx = x;

        int len = 0;
        while(xx != 0) {
            xx = xx / 10;
            len++;
        }

        xx = x;
        int[] stubs = new int[len];
        for (int i = 0; i < len; i++) {
            stubs[len-i-1] = xx % 10;
            xx = xx / 10;
        }

        for (int i = 0; i < len; i++) {
            if (i > len - i - 1) break;

            if (stubs[i] != stubs[len - i - 1]) return false;
        }

        return true;
    }
}
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