#include "combo.h"
#include<string>
#include<array>
std::string guess_sequence(int N) {
std::string pre; // constructed prefix so far
{
std::string an(N,'A');
std::string bn(N,'B');
if(press(an+bn)>0){
if(press(an)>0)
pre="A";
else
pre="B";
}else{
std::string xn(N,'X');
if(press(xn)>0)
pre="X";
else
pre="Y";
}
}
if(N==1)return pre;
char a,b,c; // the 3 nonfirst chars
{
std::array<char,4> nonfirst_chars{{'A','B','X','Y'}};
auto iter=nonfirst_chars.begin();
while(pre[0]!=*iter)
++iter;
std::swap(*iter,nonfirst_chars[0]);
a=nonfirst_chars[1];
b=nonfirst_chars[2];
c=nonfirst_chars[3];
}
while((int)pre.size()<N-1){
switch(press(pre+a+b+pre+a+c+pre+b)-pre.size()){
case 0:pre+=c;break;
case 1:pre+=b;break;
case 2:pre+=a;break;
default:__builtin_trap();
}
}
std::string tmp=pre+a;
if(press(tmp)==N)return tmp;
tmp=pre+b;
if(press(tmp)==N)return tmp;
return pre+c;
}
