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PalindromeNumber.java
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PalindromeNumber.java
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package com.company.Leetcode;
/*
https://leetcode.com/problems/palindrome-number/
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?
*/
public class PalindromeNumber {
public static boolean isPalindrome(int x) {
if (x < 0) {
return false;
}
if (x < 10) {
return true;
}
if (x % 10 == 0) {
return false;
}
int len = 0;
int tmp = x;
while (tmp != 0) {
len++;
tmp /= 10;
}
int j = len / 2;
for (int i = len - 1; i > 0; i--) {
if (j <= 0) {break;}
int a = (x / (int)Math.pow(10, i)) % 10;
int b = (x / (int) Math.pow(10, len - i - 1)) % 10;
if (a % 10 == 0) {a = 1;}
if (b == 0) { b = 1;}
if (a != b) {
return false;
}
j--;
}
return true;
}
}