D. Mahmoud and Ehab and the binary string Codeforces Round #435 (Div. 2)

http://codeforces.com/contest/862/problem/D

交互题

fflush(stdout)

调试：

先行给出结果，函数代替输入

 #include <cstdio>
 #include <cstdlib>
 #include <cmath>
 #include <cstring>
 #include <time.h>
 #include <string>
 #include <set>
 #include <map>
 #include <list>
 #include <stack>
 #include <queue>
 #include <vector>
 #include <bitset>
 #include <ext/rope>
 #include <algorithm>
 #include <iostream>
 using namespace std;
 #define ll long long
 #define minv 1e-6
 #define inf 1e9
 #define pi 3.1415926536
 #define E  2.7182818284
 const ll mod=1e9+;//
 const int maxn=1e3+;

 char str[maxn];
 int pos[],s,t,len=inf,x,y;
 char result[maxn]="01\0";
 int nn=;

 int cal()
 {
     int i,v=;
     for (i=;i<=nn;i++)
         if (str[i]!=result[i-])
             v++;
     return v;
 }

 //'l'-'r' must have num
 void work(int l,int r,int num)
 {
     if (l==r)
     {
         pos[num]=l;
         return;
     }

     int i,m=(l+r)>>;
     for (i=l;i<=m;i++)
         str[i]=((str[i]-) ^ )+;
     printf("? %s\n",str+);
     fflush(stdout);
     scanf("%d",&x);
 //        x=cal();

     for (i=l;i<=m;i++)
         str[i]=((str[i]-) ^ )+;

     if (y-x==m-l+)
     {
         pos[num]=l;
         return;
     }
     else
     {
         if (m-l+<len)
         {
             len=m-l+;
             s=l;
             t=m;
         }
     }

     if (x-y!=m-l+)
         work(l,m,num);
     else
         work(m+,r,num);
 }

 int main()
 {
     int n,i;
     scanf("%d",&n);

     for (i=;i<=n;i++)
         str[i]='';
     str[n+]='\0';
     printf("? %s\n",str+);
     fflush(stdout);
     scanf("%d",&y);
 //        y=cal();
     work(,n,);

     if (len>)
     {
         for (i=;i<=n;i++)
             str[i]='';
         str[n+]='\0';
         printf("? %s\n",str+);
         fflush(stdout);
         scanf("%d",&y);
 //            y=cal();
         if (len==inf)
             s=,t=n;
         work(s,t,);
     }

     printf("! %d %d",pos[],pos[]);
     return ;
 }