Language: C++

//1列(4通り)を質問 -> 当たったら1列（右側に）追加して(4通り)質問 -> …を繰り返すと400回以内で当たらなくなる（かendが返る）
//このとき、質問した列は黒板の右端にある。あとは、同様にして左側を特定すればよい。

#include <iostream>
#include <string>
using namespace std;

string reverse(string str) {
	string ret;
	for (int i = (int)str.length() - 1; i >= 0; i--) ret += str[i];
	return ret;
}

int n;
string query[2];

void addCharRight(int type) {
	char c0 = ((type / 2) % 2 ? '#' : '.');
	char c1 = (type % 2 ? '#' : '.');
	query[0] += c0;
	query[1] += c1;
}

void addCharLeft(int type) {
	char c0 = ((type / 2) % 2 ? '#' : '.');
	char c1 = (type % 2 ? '#' : '.');
	reverse(query[0]);
	reverse(query[1]);
	query[0] += c0;
	query[1] += c1;
	reverse(query[0]);
	reverse(query[1]);
}

void delCharRight() {
	string s[2];
	for (int i = 0; i < (int)query[0].size() - 1; i++) s[0] += query[0][i];
	for (int i = 0; i < (int)query[1].size() - 1; i++) s[1] += query[1][i];
	query[0] = s[0];
	query[1] = s[1];
}

void delCharLeft() {
	string s[2];
	for (int i = 1; i < (int)query[0].size(); i++) s[0] += query[0][i];
	for (int i = 1; i < (int)query[1].size(); i++) s[1] += query[1][i];
	query[0] = s[0];
	query[1] = s[1];
}

//return : {T, F, end}
char getQuery() {
	cout << query[0] << endl;
	cout << query[1] << endl;
	cout.flush();
	string ret[3];
	cin >> ret;
	return ret[0];
}

//return : {T, F, e}
char addQueryRight(int type) {
	addCharRight(type);
	char res = getQuery();
	if (res == 'e' || res == 'T') return res;
	delCharRight(type);
	return res;
}

char addQueryLeft(int type) {
	addCharLeft(type);
	char res = getQuery();
	if (res == 'e' || res == 'T') return res;
	delCharLeft(type);
	return res;
}

signed main() {
	cin >> n;
	
	int j;
	
	while (true) {
		for (j = 0; j < 4; j++) {
			char res = addQueryRight(j);
			if (res == 'e') return 0;
			if (res == 'T') break;
		}
		if (j == 4) break;
	}
	
	while (true) {
		for (j = 0; j < 4; j++) {
			char res = addQueryLeft(j);
			if (res == 'e') return 0;
			if (res == 'T') break;
		}
		if (j == 4) break;
	}
	return 0;
}

Compiler output:
a.cc: In function 'char getQuery()':
a.cc:57:13: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::string [3]' {aka 'std::__cxx11::basic_string<char> [3]'})
   57 |         cin >> ret;
      |         ~~~ ^~ ~~~
      |         |      |
      |         |      std::string [3] {aka std::__cxx11::basic_string<char> [3]}
      |         std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:4:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'std::string*' {aka 'std::__cxx11::basic_string<char>*'}
   57 |         cin >> ret;
      |                ^~~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'short int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(short int)((std::string*)(& ret))' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'short unsigned int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(short unsigned int)((std::string*)(& ret))' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(int)((std::string*)(& ret))' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'unsigned int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(unsigned int)((std::string*)(& ret))' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(long int)((std::string*)(& ret))' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long unsigned int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(long unsigned int)((std::string*)(& ret))' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long long int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(long long int)((std::string*)(& ret))' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: invalid conversion from 'std::string*' {aka 'std::__cxx11::basic_string<char>*'} to 'long long unsigned int' [-fpermissive]
   57 |         cin >> ret;
      |                ^~~
      |                |
      |                std::string* {aka std::__cxx11::basic_string<char>*}
a.cc:57:16: error: cannot bind rvalue '(long long unsigned int)((std::string*)(& ret))' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:57:16: error: cannot bind non-const lvalue reference of type 'void*&' to an rvalue of type 'void*'
   57 |         cin >> ret;
      |                ^~~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'std::string [3]' {aka 'std::__cxx11::basic_string<char> [3]'} to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'std::string [3]' {aka 'std::__cxx11::basic_string<char> [3]'} to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'std::string [3]' {aka 'std::__cxx11::basic_string<char> [3]'} to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(_