Submission #90366

#	Time	Username	Problem	Language	Result	Execution time	Memory
90366		Alexa2001	Arranging Tickets (JOI17_arranging_tickets)	C++17	10 / 100	7 ms	5488 KiB

arranging_tickets

#include <bits/stdc++.h>

using namespace std;

const int Nmax = 2e5 + 5;
typedef long long ll;

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

struct Edge
{
    int x, y, c;
};
vector< Edge > edges;

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

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

    for(i=1; i<=n; ++i) v[i].clear();
    for(i=1; i<=n; ++i) start[i] = 0, finish[i] = 0, add[i] = 0;

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

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

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

        start[x] += e.c;
        finish[y] += e.c;
    }


    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)
        {
            assert(heap.size());

            auto el = heap.top();
            heap.pop();

            if(dp[i] - 2 * el.second >= L)
            {
                dp[i] -= 2 * el.second;
                add[el.first] += 2 * el.second;
                need += el.second;
            }
            else
            {
                ll cat = (dp[i] - L + 1) / 2;
                dp[i] -= 2 * cat;
                add[el.first] += 2 * cat;
                need += cat;
                heap.push({el.first, el.second - cat});
            }
        }
        if(need > L) return 0;
    }

    return (need <= L);
}

bool check(ll L)
{
    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.x] += e.c;
            s[e.y] -= e.c;
        }
        else
        {
            s[e.y] += e.c;
            s[1] += e.c;
            s[e.x] -= e.c;
        }

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

    ll 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;
        edges.push_back({x, y, C});
    }

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

    ll 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: 0 / 35
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 15