Submission #31572

#	Time	Username	Problem	Language	Result	Execution time	Memory
31572		user202729	Hacker (BOI15_hac)	C++14	100 / 100	173 ms	11948 KiB

hac

// https://oj.uz/problem/view/BOI15_hac

#include <iostream>
#include <vector>
#include <deque>

typedef std::pair<int,int> ii;

int main() {
    int n;
    std::cin >> n;
    std::vector<int> value (n), segvalue (n);
    for (int& i : value) std::cin >> i;
    value.insert(value.end(), value.begin(), value.end());
//    for (int& i : value) std::cout << i << ' ';
    for (int i = 1; i < 2 * n; ++i) value[i] += value[i-1]; // conv to sum table
    int seglen = (n+1)/2;
    for (int i = 0; i < n; ++i) segvalue[i] = value[i+seglen] - value[i];
    value.clear(); // no longer need value
    segvalue.insert(segvalue.end(), segvalue.begin(), segvalue.end());
    std::deque<ii> candidatepairs; // need to calculate min of windows, then pick the max of min's
    // ii : index -> value (in segvalue)
    for (int i = 0; i < seglen-1; ++i) {
        while ((!candidatepairs.empty()) && candidatepairs.back().second >= segvalue[i])
            candidatepairs.pop_back();
        candidatepairs.emplace_back(i, segvalue[i]);
    }
    int result = -1; // need to get max
    for (int i = 0; i < n; ++i) {
        // segment [i .. i+seglen)
        // insert i+seglen-1
        int j = i+seglen-1;
        while ((!candidatepairs.empty()) && candidatepairs.back().second >= segvalue[j])
            candidatepairs.pop_back();
        candidatepairs.emplace_back(j, segvalue[j]);
        // delete anything < i
        while ((!candidatepairs.empty()) && candidatepairs.front().first < i) candidatepairs.pop_front();
        // and get the min
        result = std::max(result, candidatepairs.front().second);
    }
    std::cout << result << '\n';
}

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 40 / 40