Submission #988268

#	Time	Username	Problem	Language	Result	Execution time	Memory
988268		Wane	Combo (IOI18_combo)	C++14	100 / 100	14 ms	1976 KiB

combo

#include <bits/stdc++.h>
#include "combo.h"

//std::string guess_sequence(int N);
//extern int press(std::string p);

using namespace std;

/*
constexpr int MAX_N = 2000;
constexpr int MAX_NUM_MOVES = 8000;

void wrong_answer(const char *MSG) {
  printf("Wrong Answer: %s\n", MSG);
  exit(0);
}

std::string S;
int N;
int num_moves;

int press(std::string p) {
  if (++num_moves > MAX_NUM_MOVES) {
    wrong_answer("too many moves");
  }
  int len = p.length();
  if (len > 4 * N) {
    wrong_answer("invalid press");
  }
  for (int i = 0; i < len; ++i) {
    if (p[i] != 'A' && p[i] != 'B' && p[i] != 'X' && p[i] != 'Y') {
      wrong_answer("invalid press");
    }
  }
  int coins = 0;
  for (int i = 0, j = 0; i < len; ++i) {
    if (j < N && S[j] == p[i]) {
      ++j;
    } else if (S[0] == p[i]) {
      j = 1;
    } else {
      j = 0;
    }
    coins = std::max(coins, j);
  }
  return coins;
}
*/

std::string guess_sequence(int N) {

    string S;
    
    // 1. Get first element (2 press)
    int res = press("AB");

    if (res == 0) { // It means X or Y
        res = press("X");
        if (res == 0) S += "Y";
        else S += "X";
    }
    else {
        res = press("A");
        if (res == 0) S += "B";
        else S += "A";
    }
    //cout << "Guess: " << S << '\n';
    if (N == 1) return S;

    // 2. Get second to N - 1 element ( N - 2 press)
    char d[5] = "ABXY";
    for (int i = 1; i < N - 1; i++) { // first to N - 1, we cannot send exceeding length of 4N
        char x = 0, y = 0, z = 0;
        for (int j = 0; j < 4; j++) {
            if (d[j] == S[0]) continue;
            if (x == 0) x = d[j];
            else if (y == 0) y = d[j];
            else z = d[j];
        }

        // We can determine i'th char by using this method:
        // use delimeter as FIRST CHAR AS THEY DO NOT SHOW OFF ANYMORE
        // ALSO IT IS FIRST OF STRING, it stands special

        // SxxSxySxzSz
        // -> if 2: it has x for first, because we used all x, y, z.
        // -> if 1: it has z for first
        // -> if 0: it has y for first
        string payload = S + x + x + S + x + y + S + x + z + S + z;
        res = press(payload);
        if (res == S.size() + 2) {
            S += x;
        }
        else if (res == S.size() + 1) {
            S += z;
        } else {
            S += y;
        }
        //cout << "Guess: " << S << '\n';
    }

    // 3. Get Last element (2 press)
    int tried = 0;
    for (int j = 0; j < 4; j++) {
        if (d[j] == S[0]) continue;
        if (tried == 2) {
            S += d[j];
            return S;
        }
        res = press(S + d[j]);
        tried++;
        if (res == N) {
            S += d[j];
            return S;
        }
    }
    return S;
}

/*
int main() {
    cin >> N >> S;
    cout << guess_sequence(N) << '\n';
}
*/

Compilation message (stderr)

combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:91:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   91 |         if (res == S.size() + 2) {
      |             ~~~~^~~~~~~~~~~~~~~
combo.cpp:94:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   94 |         else if (res == S.size() + 1) {
      |                  ~~~~^~~~~~~~~~~~~~~

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