# Palindrome Number

## Problem

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

### Reversing

```
class Solution {
public boolean isPalindrome(int x) {
if (x < 0) {
return false;
}
var copy = x;
var rev = 0;
while (copy > 0) {
rev = (rev * 10) + copy % 10;
copy = copy / 10;
}
while (x > 0 || rev > 0) {
if (x % 10 != rev % 10) {
return false;
}
x = x / 10;
rev = rev / 10;
}
return x == 0 && rev == 0;
}
}
```

### Using a Deque

```
class Solution {
public boolean isPalindrome(int x) {
if (x < 0) {
return false;
}
var dq = new LinkedList<Integer>();
while (x > 0) {
dq.addLast(x % 10);
x = x / 10;
}
while (dq.size() > 1) {
if (dq.pollFirst() != dq.pollLast()) {
return false;
}
}
return true;
}
}
```