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?
Solutions
class Solution {
public boolean isPalindrome(int x) {
if (x == 0) {
return true;
}
if (x < 0) {
return false;
}
int tmp = x;
int len = 0;
while (tmp != 0) {
tmp = tmp / 10;
len++;
}
int[] stubs = new int[len];
tmp = x;
for (int i = 0; i < len; i++) {
stubs[i] = tmp % 10;
tmp = tmp / 10;
}
int lptr = 0;
int rptr = len - 1;
while (lptr < rptr) {
if (stubs[lptr++] != stubs[rptr--]) {
return false;
}
}
return true;
}
}