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?
Thoughts
- reverse num
- negative should always be false
Code(JAVA)
public boolean isPalindrome(int x) {
if (x<0)
return false;
return x == reverseNum(x);
}
private int reverseNum(int x) {
int res = 0;
while(x!=0){
res = res * 10 + x % 10;
x = x / 10;
}
return res;
}
