Submission #749383

#	Time	Username	Problem	Language	Result	Execution time	Memory
749383		adrilen	Dreaming (IOI13_dreaming)	C++17	100 / 100	111 ms	16096 KiB

dreaming

#include "dreaming.h"
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
typedef pair<int, int> pii;

constexpr int maxn = 1e5 + 5; 


bool visited[maxn] = { 0 };
int dist[maxn] = { 0 }; // Max distance to another node

basic_string <pii> adj[maxn];

pii fnd_furthest(int p, int parent)
{
    // cout << p << "\n";
    visited[p] = true;
    pii maxd = pii(p, 0);
    pii a;

    for (const pii &i : adj[p])
    {
        // cout << p << " " << i.first << "\n";
        if (i.first == parent) continue;

        a = fnd_furthest(i.first, p);
        a.second += i.second;
        if (a.second > maxd.second) {
            maxd = a;
        }
    }   
    return maxd;
}

void calc_distances(int p, int par, int d)
{
    dist[p] = max(dist[p], d);

    for (pii i : adj[p])
    {
        if (i.first == par ) continue;

        calc_distances(i.first, p, d + i.second);
    }
}

// Finds the node in the component with the minimal maximum distance
int fnd_min_max_dist(int p, int parent)
{
    
    int mind = dist[p];

    for (pii &i : adj[p])
    {
        if (i.first == parent) continue;

        if (dist[i.first] >= mind) continue;

        mind = fnd_min_max_dist(i.first, p);
    }

    return mind;
}


int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    int n = N, m = M;

    for (int i = 0; i < m; i++)
    {
        adj[A[i]].push_back(pii(B[i], T[i]));
        adj[B[i]].push_back(pii(A[i], T[i]));
    }

    vector <int> distances;
    int max_comp = 0;

    int components = 0;
    pii a, b;
    for (int i = 0; i < n; i++)
    {
        if (!visited[i])
        {
            components ++;
            a = fnd_furthest(i, -1);

            b = fnd_furthest(a.first, -1);
            a = fnd_furthest(b.first, -1);
            calc_distances(a.first, -1, 0);
            calc_distances(b.first, -1, 0);
            // cout << a.first << " " << b.first << " " << a.second << " " << fnd_min_max_dist(a.first, -1) << "\n";
            // We have now the diameter by a, b

            max_comp = max(max_comp, a.second);
            distances.emplace_back(fnd_min_max_dist(a.first, -1));

        }
    }

    // for (int i = 0; i < n; i++) cout << dist[i] << " ";
    // cout << "\n"; 


    sort(distances.begin(), distances.end(), greater<int>());

    if (components == 1)
    {
        return max_comp;
    } 

    if (components == 2)
    {
        return max({max_comp, distances[0] + distances[1] + L});
    }
    

    return max({max_comp, distances[0] + distances[1] + L, distances[2] + distances[1] + 2 * L});
}

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 18 / 18
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23