清北学堂模拟赛d4t1 a

分析：大模拟，没什么好说的.我在考场上犯了一个超级低级的错误：while (scanf（"%s",s + 1）),导致了死循环，血的教训啊，以后要记住了.

/*
    1.没有发生改变,check一下
    2.将一位1变成0
    3.添一位
    4.减一位
*/
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

int n,len,ss[3010],b[3010];
char s[3010];
bool flag = false;

bool check()
{
    int res = 0;
    for (int i = 1;i <= n; i++)
        if (ss[i] == 1)
            res += i;
        if (res % (n + 1) == 0)
            return true;
        return false;
}

bool check2()
{
    int res = 0;
    for (int i = 1; i <= n; i++)
        if (b[i] == 1)
            res += i;
        if (res % (n + 1) == 0)
            return true;
        return false;
}

void print()
{
    for (int i = 1; i <= n; i++)
        printf("%d",ss[i]);
    printf("
");
}

void add(int x,int y)
{
    memcpy(b,ss,sizeof(ss));
    for (int i = n; i > x; i--)
        b[i] = b[i-1];
        b[x] = y;
        if (check2())
        {
            memcpy(ss,b,sizeof(ss));
            flag = 1;
        }
}

void eras(int x)
{
    memcpy(b,ss,sizeof(ss));
    for (int i = x; i <= n; i++)
        b[i] = b[i + 1];
    if (check2())
    {
        memcpy(ss,b,sizeof(ss));
        flag = 1;
    }
}

int main()
{
    scanf("%d",&n);
    while(scanf("%s",s + 1) != EOF)
    {
        memset(b,0,sizeof(b));
        len = strlen(s + 1);
        flag = false;
        if (abs(n - len) > 1)
        {
            printf("-1
");
            continue;
        }
        for (int i = 1; i <= len; i++)
            ss[i] = s[i] - '0';
            if (n == len)
            {
        if (check())  //1
        {
            print();
            continue;
        }
        for (int i = 1; i <= n; i++) //2
        {
            if (ss[i] == 1)
            {
                ss[i] = 0;
                if (check())
                {
                    flag = 1;
                    break;
                }
                ss[i] = 1;
            }
        }
        }
        if (flag)
        {
            print();
            continue;
        }
        if (len == n - 1)
        {
        for (int i = 1; i <= n + 1; i++) //3
        for (int j = 0; j <= 1; j++)
        {
            add(i,j); //i位以及以后都要往后挪1
            if (flag)
            break;
        }
        }
        if (flag)
        {
            print();
            continue;
        }
        if (len == n + 1)
        {
        for (int i = 1; i <= n; i++)
        {
            eras(i);
            if (flag)
            break;
        }
        }
        if (flag)
        {
            print();
            continue;
        }
        printf("-1
");
    }

    return 0;
}