Submission #477061

#	Time	Username	Problem	Language	Result	Execution time	Memory
477061		Genius3435	Combo (IOI18_combo)	C++17	100 / 100	37 ms	528 KiB

combo

#include "combo.h"

#include <algorithm>
#include <string>

std::string guess_sequence(int N) {
	std::string cur;
	if (press("AB")) {
		if (press("A")) cur = "A";
		else cur = "B";
	} else {
		if (press("X")) cur = "X";
		else cur = "Y";
	}

	std::string poss = "ABXY"; poss.erase(poss.find(cur[0]), 1);
	const char A = poss[0], B = poss[1], X = poss[2];


	while ((int) cur.size()+2 <= N) {
		// Let s = cur, A,B,X = poss
		// Try sAA + sAB + sBA
		int p = press(cur+A+A + cur+A+B + cur+B+A);
		const int sz = cur.size();
		if (p == sz) {
			// Next char is X
			cur += X;
		}
		else if (p == sz+1) {
			// Next chars are AX,BB,BX
			p = press(cur+B+B);
			if (p == sz+2) cur += B, cur += B;
			else if (p == sz+1) cur += B, cur += X;
			else cur += A, cur += X;
		}
		else {
			// Next chars are AA,AB,BA
			p = press(cur+A+A);
			if (p == sz+2) cur += A, cur += A;
			else if (p == sz+1) cur += A, cur += B;
			else cur += B, cur += A;
		}
	}

	if (N == (int) cur.size()) return cur;

	if (press(cur+A) == N) return cur+A;
	else if (press(cur+B) == N) return cur+B;
	else return cur+X;
}

• Subtask 1: 5 / 5
• Subtask 2: 95 / 95