9. Palindrome Number(判断一个整数是否为回文数)

官网

Determine whether an integer is a palindrome. Do this without extra space.

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Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem “Reverse Integer”, you know that the reversed integer might overflow. How would you handle such case?

题目大意

1.不能用额外的空间，不能转化为string在判断。

2.如果反转数字记得判断范围。

解题思路

1.反转数字在计算

AC代码（java）

package test;
class Solution {
public boolean isPalindrome(int x) {
if(x<0)return false;
if(x<10)return true;
if(x%10==0)return false;
long   reverse = 0,tem = x;
while(x!=0){
reverse = reverse*10 + x%10;
x /= 10;
}
if(reverse == tem){
return true;
}else{
return false;
}
}
}
public class test {
public  static void main(String[] args){
int a = 1221;
Solution b = new Solution();
if(b.isPalindrome(a)){
System.out.println("yes!");
}else{
System.out.println("no!");
}
}
}