• Ppalindrome Number
  Determine whether an integer is a palindrome. Do this without extra space.
  Some hints:
  Could negative integers be palindromes? (ie, -1)
  If yu 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.
• 題目大意：判斷一個整數是否是迴文數字，不要使用額外的空間。
• 思路：反轉這個整數，看與原來的數字是否相等。
• 程式碼：

#include<iostream>
using namespace std;
// 方法一
bool isPalindrome(int x)
{
    if(x<0 || x%10==0&&x!=0)return false;
    long y = x;
    long temp=0;
    while(y>0)
    {
        temp = temp*10+y%10;
        y/=10;
    }
    return temp==x;
}
int main()
{
    int x;
    cin>>x;
    if(isPalindrome(x))
    {
        cout<<"是迴文數字"<<endl;
    }
    else
    {
        cout<<"不是迴文數字"<<endl;
    }
    return 0;
}
 

    //方法二
    bool isPalindrome(int x)
    {
        if(x<0)return false;
        char ch[100];
        int k=0;
        while(x>0)
        {
            ch[k++] = char(x%10+'0');
            x/=10;
        }
        ch[k]='\0';
        k--;
        for(int i=0;i<k;i++,k--)
        {
            if(ch[i]!=ch[k])return false;
        }
        return true;
    }
 

• 以上。

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