Palindrome Number
Created: February 17, 2019 by [lek-tin]
Last updated: February 17, 2019
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:
Could you solve it without converting the integer to a string?
Solution:
Convert the number to string
class Solution {
public boolean isPalindrome(int x) {
String num = Integer.toString(x);
for (int i = 0; i < num.length() / 2; i++) {
if (num.charAt(i) != num.charAt(num.length() - 1 - i)) return false;
}
return true;
}
}
Iterate over each digit and then reconstruct the new number.
class Solution {
public boolean isPalindrome(int x) {
if (x < 0) {
return false;
}
if (x < 10) {
return true;
}
int oldNum = x;
int newNum = 0;
while (x > 0) {
newNum = newNum * 10 + x % 10;
x = x / 10;
}
return oldNum == newNum ? true : false;
}
}