[LeetCode]9.Palindrome Number

Some hints:

Could negative integers be palindromes? (ie, ⑴)

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?

There is a more generic way of solving this problem.

/*********************************
* 日期：2015-01⑵0
* 作者：SJF0115
* 题目: 9.Palindrome Number
* 网址：https://oj.leetcode.com/problems/palindrome-number/
* 结果：AC
* 来源：LeetCode
* 博客：
**********************************/
#include <iostream>
using namespace std;

class Solution {
public:
bool isPalindrome(int x) {
// negative integer
if(x < 0){
return false;
}//if
int tmp = x;
int n = 0;
// reverse an integer
while(tmp){
n = n * 10 + tmp % 10;
tmp /= 10;
}//while
return (x == n);
}
};

int main(){
Solution solution;
int num = 1234321;
bool result = solution.isPalindrome(num);
// 输出
cout<<result<<endl;
return 0;
}

class Solution {
public:
bool isPalindrome(int x) {
// negative integer
if(x < 0){
return false;
}//if
// 位数
int divisor = 1;
while(x / divisor >= 10){
divisor *= 10;
}//while
int first,last;
while(x){
first = x / divisor;
last = x % 10;
// 高位和低位比较 是不是相等
if(first != last){
return false;
}//if
// 去掉1个最高位和1个最低位
x = x % divisor / 10;
divisor /= 100;
}//while
return true;
}
};