题目描述
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.
My solution(10ms,36.5MB)
整形转换成字符型，然后进行颠倒转换
class Solution {
public boolean isPalindrome(int x) {
if(x<0){
return false;
}else{
String a = x + "";
String aReverse = new StringBuilder(a).reverse().toString();
if(a.equals(aReverse)){
return true;
}else{return false;}
}
}
}Other solution(6ms,35.1MB):
这个方法很神奇啊！Ψ(￣∀￣)Ψ
先排除负数，然后把整数分成两个部分，x为前一半，rev为后一半，例：32499423
并且rev还是已经倒转过后的数字，即3249
最后比较一下两个是否相同
如果是奇数个数字，例：12321
则rev为123，x为12
然后比较123/10=12和12是否相等
class Solution {
public boolean isPalindrome(int x) {
if (x<0 || (x!=0 && x%10==0)) return false;
int rev = 0;
while (x>rev){
rev = rev*10 + x%10;
x = x/10;
}
return (x==rev || x==rev/10);
}
}