The 30th International Olympiad in Informatics was held in Tsukuba, Japan in 2018. There were two competition days, with 3 problems given to the competitors on each day. You can see Combo problem and solutions below.
Problem :
ioi2018problem1Solution :
#include "combo.h"
#include <bits/stdc++.h>
using namespace std;
string guess_sequence(int N) {
string p = "";
if(press("AB") >= 1) p = press("A") ? "A" : "B";
else p = press("X") ? "X" : "Y";
vector<char> chr = {'A', 'B', 'X', 'Y'};
chr.erase(find(chr.begin(), chr.end(), p[0]));
while((int)p.size() <= N - 2){
int query = press(p + chr[0] + chr[0] + p + chr[0] + chr[1] + p + chr[1] + chr[0]);
if(query == p.size()){
p.push_back(chr[2]);
}
else if(query == p.size() + 1){
query = press(p + chr[1] + chr[2]);
if(query == p.size()) p = p + chr[0] + chr[2];
else if(query == p.size() + 1) p = p + chr[1] + chr[1];
else p = p + chr[1] + chr[2];
}
else{
query = press(p + chr[0] + chr[1]);
if(query == p.size()) p = p + chr[1] + chr[0];
else if(query == p.size() + 1) p = p + chr[0] + chr[0];
else p = p + chr[0] + chr[1];
}
}
while(p.size() != N){
if(press(p + chr[0]) == p.size() + 1) p.push_back(chr[0]);
else if(press(p + chr[1]) == p.size() + 1) p.push_back(chr[1]);
else p.push_back(chr[2]);
}
return p;
}
Explanation :
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