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?
public boolean isPalindrome(int x) {
if(x < 0) {
return false;
}
int res = 0;
int y = x;
while(y != 0) {
res = res * 10 + y % 10;
y /= 10;
}
if(res == x) {
return true;
} else {
return false;
}
}
}
或者
class Solution {
public boolean isPalindrome(int x) {
String s = x + "";
int l = 0, r = s.length() - 1;
while (l < r) {
if (s.charAt(l) != s.charAt(r)) return false;
l++;
r--;
}
return true;
}
}
第一个方法：
Time Complexity = O(log(x)) 以十为底
Space Complexity = O(1)
