Submission #393817

#	Time	Username	Problem	Language	Result	Execution time	Memory
393817		ruadhan	Combo (IOI18_combo)	C++17	100 / 100	54 ms	580 KiB

combo

    #include "combo.h"
    #include <bits/stdc++.h>
    using namespace std;
     
    string guess_sequence(int n) {
        string ans;
        ans.reserve(n);
     
        array a = {'A', 'B', 'X', 'Y'};
     
        // call `press` 2 times
        auto guess_endpoint = [&]() {
            if (press(ans + a[0] + ans + a[1]) == int(ans.size()))
                ans += press(ans + a[2]) == int(ans.size()) ? a[3] : a[2];
            else
                ans += press(ans + a[0]) == int(ans.size()) ? a[1] : a[0];
        };
        auto guess_mid = [&]() {
            int matched = press(ans + a[0] + a[0] + ans + a[0] + a[1] + ans + a[0] + a[2] + ans + a[1]) - int(ans.size());
            if (matched == 0)
                ans += a[2];
            else if (matched == 1)
                ans += a[1];
            else
                ans += a[0];
        };
     
        // call `press` 2 + (n - 2) + 2
     
        // first
        guess_endpoint();
        if (n == 1) return ans;
     
        *find(a.begin(), a.end(), ans[0]) = 'Y';
     
        // n - 2
        for (int i = n - 2; i; --i)
            guess_mid();
     
        // last
        if (n != 1) guess_endpoint();
        return ans;
    }

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