Submission #740339

#	Time	Username	Problem	Language	Result	Execution time	Memory
740339		GrindMachine	Combo (IOI18_combo)	C++17	100 / 100	47 ms	604 KiB

combo

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

got 97, couldnt optimize to 100
to optimize, note that we only need 2 (not 3) queries to find the first char
this can be done using dnc approach

*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

#include "combo.h"

string guess_sequence(int n) {
    string chars = "ABXY";
    string s = "";
    char first = '?';

    if (press("AB")) {
        if (press("A")) {
            first = 'A';
        }
        else {
            first = 'B';
        }
    }
    else {
        if (press("X")) {
            first = 'X';
        }
        else {
            first = 'Y';
        }
    }

    s.pb(first);
    chars.erase(find(all(chars), first));

    if (n == 1) {
        return s;
    }

    while (sz(s) < n - 1) {
        int siz = sz(s);

        string t = s + chars[0];
        trav(ch, chars) {
            t = t + s + chars[1] + ch;
        }

        int res = press(t);

        if (res == siz + 0) {
            s.pb(chars[2]);
        }
        else if (res == siz + 1) {
            s.pb(chars[0]);
        }
        else {
            s.pb(chars[1]);
        }
    }

    rep(j, 2) {
        s.pb(chars[j]);
        if (press(s) == n) {
            return s;
        }
        s.pop_back();
    }

    s.pb(chars.back());
    return s;
}

Compilation message (stderr)

combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:95:18: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   95 |     while (sz(s) < n - 1) {
      |                  ^

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