Submission #1205879

#	Time	Username	Problem	Language	Result	Execution time	Memory
1205879		kitkat12	Combo (IOI18_combo)	C++20	100 / 100	7 ms	504 KiB

combo

// Problem URL: https://oj.uz/problem/view/IOI18_combo
// Start Time: 5/22/2025, 1:37:39 PM

#include <bits/stdc++.h>
#include "combo.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define mp make_pair
#define pb push_back
#define F first
#define S second
#define debug(x) std::cout << #x << ": " << x << "\n"
#define all(v) v.begin(), v.end()
#define li(i,a,b) for (int i = a; i < b; i++)
#define endl '\n'
#define mem(name,val) memset(name,val,sizeof(name))
#define min(a,b) (a<=b ? a : b)
#define max(a,b) (a>=b ? a : b)

string guess_sequence(int n)
{
    vector<char> abc = {'A','B','X','Y'};

    int r = press("AB");          
    char first;
    if (r) {                
        first = press("A") ? 'A' : 'B';
    } else {                     
        first = press("X") ? 'X' : 'Y';
    }
    string pref(1, first);

    vector<char> rest;
    for (char c : abc) if (c != first) rest.push_back(c);

    const char p = rest[0];  
    const char q = rest[1];
    const char r_ = rest[2]; 

    for (int i = 1; i < n - 1; ++i) {
        string qstr;
        qstr.reserve((i + 1) * 4 + 3);

        qstr += pref; qstr.push_back(p);
        qstr += pref; qstr.push_back(q); qstr.push_back(q);
        qstr += pref; qstr.push_back(q); qstr.push_back(p);
        qstr += pref; qstr.push_back(q); qstr.push_back(r_);

        int k = press(qstr);
        int delta = k - (int)pref.size();
        if      (delta == 0) pref.push_back(r_); 
        else if (delta == 1) pref.push_back(p);    
        else                 pref.push_back(q);                         
        // int k = press(qstr);
        // if (k == pref.size() + 1)      pref.push_back(p);
        // else if (k == pref.size() + 2) pref.push_back(r_);
        // else                           pref.push_back(q);
    }
    if (n == 1) return pref;

    string try1 = pref + q + pref + p; 
    int k = press(try1);

    if (k == n - 1) {                    
        pref.push_back(r_);
    } else {             
        pref.push_back(press(pref + q) == n ? q : p);
    }
    return pref;
}

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