IOI '13 P4 - Cave

#include "cave.h"
#include <iostream>
#include <vector>
#include <set>
#include <algorithm>

using namespace std;

void exploreCave(int N) {
    int query[N] {};
    set<int> indices;
    for (int i = 0; i < N; ++i) indices.insert(i);

    int correctPos[N], door[N];

    // find switch of each door in order of doors
    for (int d = 0; d < N; ++d) {
        // find correct position of door
        vector<int> v(indices.begin(), indices.end());
        int n = N-d;
        for (int i : v) query[i] = 0;
        int correct = (tryCombination(query) == d ? 1 : 0);

        int left = 0, right = n;
        while (right - left > 1) {
            int mid = (left + right) / 2;
            for (int i = left; i < mid; ++i) query[v[i]] = correct;
            for (int i = mid; i < right; ++i) query[v[i]] = 1-correct;
            if (tryCombination(query) == d) left = mid;
            else right = mid;
        }
        door[v[left]] = d;
        correctPos[v[left]] = correct;
        indices.erase(v[left]);
        query[v[left]] = correct;
    }
    answer(correctPos, door);
}