Submission #442495

#	Time	Username	Problem	Language	Result	Execution time	Memory
442495		zxcvbnm	Dreaming (IOI13_dreaming)	C++14	100 / 100	202 ms	16012 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
struct Edge {
    int to, w;
    bool operator<(const Edge& other) const {
        return w < other.w;
    }
};
const int maxN = 1e5 + 5;
const int INF = 1e9 + 5;

int n, m;
vector<Edge> adj[maxN];
vector<int> comp[maxN];
vector<pair<int, int>> centers;
int ccs = 0;
bool vis[maxN];
int dist[maxN];
int par[maxN];

void dfs(int v) {
    vis[v] = true;
    comp[ccs].push_back(v);
    for(Edge u : adj[v]) {
        if (!vis[u.to]) {
            dfs(u.to);
        }
    }
}

pair<int, int> mx(int from, int idx) {
    priority_queue<Edge> q;
    q.push({from, 0});
    for(int i : comp[idx]) {
        dist[i] = INF;
    }
    for(int i : comp[idx]) {
        par[i] = -1;
    }
    dist[from] = 0;

    while(!q.empty()) {
        Edge v = q.top();
        q.pop();
        if (v.w > dist[v.to]) continue;

        for(Edge u : adj[v.to]) {
            int d = dist[v.to] + u.w;
            if (d < dist[u.to]) {
                dist[u.to] = d;
                par[u.to] = v.to;
                q.push({u.to, dist[u.to]});
            }
        }
    }

    pair<int, int> ret = {-1, -1};
    for(int i : comp[idx]) {
//        cout << i << " " << dist[i] << "\n";
        if (dist[i] > ret.second) {
            ret = {i, dist[i]};
        }
    }
    assert(ret.second != -1);
    assert(ret.second != INF);
    return ret;
}

void find_center(int idx) {
    int y = mx(comp[idx][0], idx).first;
    pair<int, int> p = mx(y, idx);
    int z = p.first;
    int path = p.second;

    int curr = path, center = -1;
    for(int i = 0; i < n; i++) {
        if (max(dist[z], path-dist[z]) <= curr) {
            curr = max(dist[z], path-dist[z]);
            center = z;
        }
        z = par[z];
        if (z == -1) break;
    }
    centers.push_back({curr, center});
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    n = N, m = M;
    for(int i = 0; i < M; i++) {
        adj[A[i]].push_back({B[i], T[i]});
        adj[B[i]].push_back({A[i], T[i]});
    }

    int sum = 0;
    for(int i = 0; i < N; i++) {
        if (!vis[i]) {
            dfs(i);
            find_center(ccs);
            ccs++;
        }
    }

    sort(centers.rbegin(), centers.rend());
    for(int i = 1; i < (int) centers.size(); i++) {
        adj[centers[0].second].push_back({centers[i].second, L});
        adj[centers[i].second].push_back({centers[0].second, L});
//        cout << centers[0].second << " " << centers[i].second << "\n";
    }

    for(int i = 1; i < ccs; i++) {
        for(int j : comp[i]) {
            comp[0].push_back(j);
        }
    }

    return mx(mx(0, 0).first, 0).second;
}

Compilation message (stderr)

dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:95:9: warning: unused variable 'sum' [-Wunused-variable]
   95 |     int sum = 0;
      |         ^~~

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