Submission #393652

#	Time	Username	Problem	Language	Result	Execution time	Memory
393652		phathnv	Combo (IOI18_combo)	C++11	0 / 100	37 ms	204 KiB

combo

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

using namespace std;

string guess_sequence(int n) {
    string s;
    char ch[4] = {'A', 'B', 'X', 'Y'};
    int l = 0, r = 3;
    while (l < r){
        int mid = (l + r) >> 1;
        string tmp;
        for(int i = l; i <= mid; i++)
            tmp.push_back(ch[i]);
        if (press(tmp) > 0)
            r = mid;
        else
            l = mid + 1;
    }
    swap(ch[0], ch[l]);
    for(int t = 1; t <= 2; t++){
        s.push_back(ch[0]);
        for(int i = 2; i <= n; i++)
            s.push_back(ch[t]);
    }
    int lastPress = press(s);
    for(int i = 2; i <= n; i++){
        if (lastPress < i){
            s[i - 1] = s[i + n - 1] = ch[3];
            lastPress = press(s);
        } else {
            s[i + n - 1] = ch[1];
            int tmp = press(s);
            if (tmp < lastPress)
                s[i - 1] = s[i + n - 1] = ch[2];
            else
                lastPress = tmp;
        }
    }

    return s.substr(0, n);
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 95