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?
class Solution {
public:
bool isPalindrome1(int x) {
//负数和以10的倍数肯定不是对称数
if(x<0||(x>0&&x%10==0))
return false;
string num = to_string(x);
int size = num.size();
for(int i=0;i<size/2;i++){
if(num[i]!=num[size-1-i])
{
return false;
}
}
return true;
}
bool isPalindrome(int x) {
//使用反转一半长度并比较的方式
if(x<0|| (x!=0 &&x%10==0)) return false;
int sum=0;
while(x>sum)
{
sum = sum*10+x%10;
x = x/10;
}
return (x==sum)||(x==sum/10);
}
};
