Submission #90361

#	Time	Username	Problem	Language	Result	Execution time	Memory
90361		Alexa2001	Arranging Tickets (JOI17_arranging_tickets)	C++17	85 / 100	677 ms	32880 KiB

arranging_tickets

#include <bits/stdc++.h>

using namespace std;

const int Nmax = 2e5 + 5;

priority_queue<int> heap;
int start[Nmax], finish[Nmax], add[Nmax], dp[Nmax], s[Nmax];
vector<int> v[Nmax];
int n, m, i, A, B;
vector< pair<int,int> > edges;

int mod(int x)
{
    if(x <= 0) return x+n;
    if(x>n) return x-n;
    return x;
}

bool check_center(int where, int L)
{
    int i, need = 0, nr;

    for(i=1; i<=n; ++i) v[i].clear();

    for(auto e : edges)
    {
        int x, y;
        x = mod(e.first - where + 1);
        y = mod(e.second - where + 1);

        if(x > y) swap(x, y);
        v[x].push_back(y);
    }

    while(heap.size()) heap.pop();

    for(i=1; i<=n; ++i) finish[i] = 0;

    for(i=1; i<=n; ++i)
    {
        start[i] = v[i].size(); add[i] = 0;
        for(auto it : v[i]) finish[it] ++;
    }

    dp[0] = L;
    for(i=1; i<n; ++i)
    {
        for(auto it : v[i]) heap.push(it);

        dp[i] = dp[i-1] + start[i] - finish[i] + add[i];

        while(dp[i] > L && need <= L)
        {
            assert(heap.size());

            dp[i] -= 2;
            nr = heap.top();
            heap.pop();
            add[nr] += 2;
            ++need;
        }

        if(need > L) return 0;
    }

    return (need <= L);
}

bool check(int L)
{
    int i;
    for(i=1; i<=n; ++i)
        return (check_center(A, L) || check_center(B, L));
}

int best_point(bool dir)
{
    int i;
    for(i=1; i<=n; ++i)
        s[i] = 0;

    for(auto e : edges)
        if(dir == 0)
        {
            ++s[e.first];
            --s[e.second];
        }
        else
        {
            ++s[e.second];
            ++s[1];
            --s[e.first];
        }

    for(i=1; i<=n; ++i) s[i] += s[i-1];

    int Max = 0;
    for(i=1; i<=n; ++i) Max = max(Max, s[i]);
    for(i=1; i<=n; ++i)
        if(Max == s[i]) return mod(i+1);
}

int main()
{
 //   freopen("input", "r", stdin);

    cin >> n >> m;

    int i, x, y, C;
    for(i=1; i<=m; ++i)
    {
        cin >> x >> y >> C;
        if(x > y) swap(x, y);
        edges.push_back({x, y});
    }

    A = best_point(0);
    B = best_point(1);

    int st = 0, dr = m, mid;
    while(st <= dr)
    {
        mid = (st+dr) / 2;
        if(check(mid)) dr = mid - 1;
            else st = mid + 1;
    }

    cout << st << '\n';
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 35 / 35
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 0 / 15