CodeForces 625D Finals in arithmetic

神奇的构造题，我的思路比较奇葩。搞了好久，看到WA on 91我绝望了，然后自己造数据，找到了错误，总算是AC了，现在是凌晨0：24分，看到AC之后，感动China！

我写的代码无比的长。。。。。应该有很简单的方法吧。。。。。没想到。

#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <queue>
#include <stack>
#include <map>
#include <vector>
using namespace std;

const int maxn =  + ;
char s[maxn];
int a[maxn], b[maxn], sum[maxn], flag[maxn];
int tmpa[maxn], tmpb[maxn], ans[maxn];
int nb[maxn];
int len;

void read()
{
    scanf("%s", s);
    for (int i = ; s[i]; i++) b[i + ] = s[i] - '';
    nb[] = b[] *  + b[]; for (int i = ; s[i]; i++) nb[i] = s[i] - '';
}

void init()
{
    len = strlen(s);
    memset(flag, , sizeof flag);
}

bool check1()
{
    for (int i = ; i <= (len + ) / ; i++)
    {
        if (sum[i] %  == ) a[i] = sum[i] / , a[len - i + ] = sum[i] / ;
        else a[i] = sum[i] /  + , a[len - i + ] = sum[i] - a[i];
    }

    for (int i = ; i <= len; i++) tmpa[i] = a[i];
    for (int i = ; i <= len; i++) tmpb[i] = a[len - i + ];

    int k = ;
    for (int i = ; i <= len; i++)
    {
        ans[i] = (tmpa[i] + tmpb[i] + k) % ;
        k = (tmpa[i] + tmpb[i] + k) / ;
    }

    for (int i = ; i <= len; i++)
    if (b[len - i + ] != ans[i]) return ;
    return ;
}

bool work1()
{
    bool fail = ; init();

    for (int i = len; i >= len /  + ; i--)
    {
        int id_now = i, id_pre = len - i + ;

        if (i == len)
        {
            if (b[i] == ) { fail = ; break; }

            sum[id_now] = b[id_now]; sum[id_pre] = b[id_now];
            flag[id_now] = ; flag[id_pre] = ;

            if (b[id_now] == b[id_pre]) flag[id_pre + ] = ;
            else if (b[id_now] +  == b[id_pre]) flag[id_pre + ] = ;
            else { fail = ; break; }
        }

        else
        {
            int num_now, num_pre;
            num_now = b[id_now] - flag[id_now + ];

            if (num_now == )
            {
                if (b[id_pre] == )
                {
                    sum[id_now] = ; sum[id_pre] = ;
                    flag[id_pre + ] = ;
                }
                else if (b[id_pre] == )
                {
                    sum[id_now] = ; sum[id_pre] = ;
                    flag[id_pre + ] = ;
                }
                else { fail = ; break; }
            }
            else if (b[id_now] ==  && flag[id_now + ])
            {
                if (b[id_pre] ==  || b[id_pre] == )
                {
                    flag[id_now] = ;
                    if (b[id_pre] == ) flag[id_pre + ] = ;
                    sum[id_now] = ;
                    sum[id_pre] = ;
                }
                else { fail = ; break; }
            }
            else
            {
                num_now = num_now + flag[id_pre] * ;
                num_pre = b[id_pre] + flag[id_pre] * ;

                if (num_now == num_pre)
                {
                    flag[id_pre + ] = ;
                    sum[id_now] = num_now; sum[id_pre] = num_now;
                    if (num_now >= ) flag[id_now] = ;
                }

                else if (num_now +  == num_pre)
                {
                    flag[id_pre + ] = ;
                    sum[id_now] = num_now; sum[id_pre] = num_now;
                    if (num_now >= ) flag[id_now] = ;
                }
                else { fail = ; break; }
            }
        }
        if (id_now == id_pre&&sum[id_pre] %  != ) { fail = ; break; }
    }

    if (!check1()) fail = ;

    return fail;
}

bool check2()
{
    memset(tmpa, , sizeof tmpa);
    memset(tmpb, , sizeof tmpb);

    for (int i = ; i <= (len + ) / ; i++)
    {
        if (sum[i] %  == ) a[i] = sum[i] / , a[len - i + ] = sum[i] / ;
        else a[i] = sum[i] /  + , a[len - i + ] = sum[i] - a[i];
    }

    for (int i = ; i <= len; i++) tmpa[i] = a[i];
    for (int i = ; i <= len; i++) tmpb[i] = a[len - i + ];

    int k = ;
    len++;
    for (int i = ; i <= len; i++)
    {
        ans[i] = (tmpa[i] + tmpb[i] + k) % ;
        k = (tmpa[i] + tmpb[i] + k) / ;
    }

    for (int i = ; i <= len; i++)
    if (b[len - i + ] != ans[i]) return ;
    return ;
}

bool work2()
{
    bool fail = ; init();

    len--;

    for (int i = len; i >= len /  + ; i--)
    {
        int id_now = i, id_pre = len - i + ;

        if (i == len)
        {
            sum[id_now] =  + nb[id_now]; sum[id_pre] =  + nb[id_now];
            flag[id_now] = ; flag[id_pre] = ;

            if (nb[id_now] +  == nb[id_pre]) flag[id_pre + ] = ;
            else if (nb[id_now] +  +  == nb[id_pre]) flag[id_pre + ] = ;
            else { fail = ; break; }
        }

        else
        {
            int num_now, num_pre;
            num_now = nb[id_now] - flag[id_now + ];

            if (num_now == )
            {
                if (nb[id_pre] == )
                {
                    sum[id_now] = ; sum[id_pre] = ;
                    flag[id_pre + ] = ;
                }
                else if (nb[id_pre] == )
                {
                    sum[id_now] = ; sum[id_pre] = ;
                    flag[id_pre + ] = ;
                }
                else { fail = ; break; }
            }
            else if (nb[id_now] ==  && flag[id_now + ])
            {
                if (nb[id_pre] ==  || nb[id_pre] == )
                {
                    flag[id_now] = ;
                    if (nb[id_pre] == ) flag[id_pre + ] = ;
                    sum[id_now] = ;
                    sum[id_pre] = ;
                }
                else { fail = ; break; }
            }
            else
            {
                num_now = num_now + flag[id_pre] * ;
                num_pre = nb[id_pre] + flag[id_pre] * ;

                if (num_now == num_pre)
                {
                    flag[id_pre + ] = ;
                    sum[id_now] = num_now; sum[id_pre] = num_now;
                    if (num_now >= ) flag[id_now] = ;
                }

                else if (num_now +  == num_pre)
                {
                    flag[id_pre + ] = ;
                    sum[id_now] = num_now; sum[id_pre] = num_now;
                    if (num_now >= ) flag[id_now] = ;
                }
                else { fail = ; break; }
            }
        }
        if (id_now == id_pre&&sum[id_pre] %  != ) { fail = ; break; }
    }

    if (!check2()) fail = ;

    return fail;
}

int main()
{
    read();
    init();
    if (!work1())
    {
        for (int i = ; i <= len; i++) printf("%d", a[i]);
        printf("\n");
    }
    else
    {
        if (b[] == )
        {
            if (!work2())
            {
                for (int i = ; i <= len - ; i++) printf("%d", a[i]);
                printf("\n");
            }
            else { printf("0\n"); }
        }
        else { printf("0\n"); }
    }
    return ;
}