POJ 2402 Palindrome Numbers

题目链接

水题，LA我居然没找到在那里。

#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <iostream>
using namespace std;
#define LL long long
LL dp[50],bin[50];
int que[31],s;
void judge(int x)
{
    s = 0;
    while(x)
    {
        que[s++] = x%10;
        x /= 10;
    }
}
int main()
{
    int i;
    LL temp,n,x;
    temp = 1;
    bin[0] = 1;
    for(i = 1;i <= 10;i ++)
    bin[i] = 10*bin[i-1];
    for(i = 1;i <= 20;i ++)
    {
        if(i%2 == 1)
        {
            dp[i] = temp*9;
            temp *= 10;
        }
        else
        {
            dp[i] = dp[i-1];
        }
    }
    while(cin>>n&&n)
    {
        for(i = 1;i <= 20;i ++)
        {
            if(n > dp[i])
            n -= dp[i];
            else
            {
                if(i == 1)
                cout<<n<<endl;
                else if(i == 2)
                cout<<n<<n<<endl;
                else if(i%2 == 1)
                {
                    x = bin[i/2] + n - 1;
                    cout<<x;
                    judge(x);
                    for(i = 1;i < s;i ++)
                    cout<<que[i];
                    cout<<endl;
                }
                else
                {
                    x = bin[i/2-1] + n - 1;
                    cout<<x;
                    judge(x);
                    for(i = 0;i < s;i ++)
                    cout<<que[i];
                    cout<<endl;
                }
                break;
            }
        }
    }
    return 0;
}