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IsPalindrome.java
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53 lines (46 loc) · 1.35 KB
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package org.leetcode;
/**
* 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?
*/
public class IsPalindrome {
public static void main(String[] args) {
System.out.println(isPalindrome(120232021));
}
public static boolean isPalindrome(int x) {
// Negative numbers are not palindromes
if (x < 0 || (x % 10 == 0 && x != 0)) {
return false;
}
int reversedHalf = 0;
while (x > reversedHalf) {
reversedHalf = reversedHalf * 10 + x % 10; // Move last digit of x to reversedHalf
x /= 10; // Remove the last digit of x
}
// If x is equal to reversedHalf, or if x is equal to reversedHalf/10 for odd-length numbers
return x == reversedHalf || x == reversedHalf / 10;
}
}