Submission #778656

#	Time	Username	Problem	Language	Result	Execution time	Memory
778656		benjaminkleyn	The Big Prize (IOI17_prize)	C++17	100 / 100	525 ms	2568 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>
using namespace std;

bool asked[200000] = {false};
int L[200000], R[200000];

unordered_map<int, set<int>> queries;

bool Ask(int i)
{
    if (asked[i]) return L[i] + R[i] == 0;
    
    asked[i] = true;
    vector<int> res = ask(i);
    L[i] = res[0], R[i] = res[1];

    if (queries.find(L[i] + R[i]) == queries.end())
        queries[L[i] + R[i]] = set<int>();
    queries[L[i] + R[i]].insert(i);

    return L[i] + R[i] == 0;
}


int Find(int l, int r)
{
    if (l + 1 == r)
        return -1;

    for (auto [x, s] : queries)
    {
        auto it1 = s.upper_bound(l), it2 = s.lower_bound(r);
        if (it1 == s.begin() || it2 == s.end()) continue;
        if (L[*prev(it1)] == L[*it2]) return -1;
    }

    int m = (l + r) / 2;
    if (Ask(m)) return m;

    int x = Find(l, m);
    if (x >= 0) return x;

    int y = Find(m, r);
    if (y >= 0) return y;

    return -1;
}

int find_best(int n) 
{
    if (Ask(0)) return 0;
    if (Ask(n-1)) return n-1;
    return Find(0, n - 1);
}

• Subtask 1: 20 / 20
• Subtask 2: 80 / 80