Submission #1347146

#TimeUsernameProblemLanguageResultExecution timeMemory
1347146nicolo_010Dreaming (IOI13_dreaming)C++20
0 / 100
30 ms12508 KiB
#include <bits/stdc++.h>
#include "dreaming.h"
using namespace std;
using ll = long long;
using pii = pair<int, int>;

vector<int> h;
int n;
vector<vector<pii>> adj;
vector<bool> vis;

void dfs(int u, int p=-1, int w=0) {
    h[u] = w;
    for (auto [v, pe] : adj[u]) {
        if (v==p) continue;
        dfs(v, u, w+pe);
    }
}

int t;
vector<int> comp;

void dfs1(int u, int p=-1) {
    comp.push_back(u);
    for (auto [v, w] : adj[u]) {
        if (v==p) continue;
        dfs1(v, u);
    }
}

int travelTime(int N, int m, int L, int A[], int B[], int T[]) {
    t=0;
    n = N;
    adj.assign(n, {});
    vector<vector<int>> cmp;
    vis.assign(n, false);
    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]});
    }
    for (int i=0; i<n; i++) {
        if (!vis[i]) {
            comp.clear();
            dfs1(i);
            cmp.push_back(comp);
            for (auto x : comp) {
                vis[x] = true;
            }
        }
    }
    int k = cmp.size();
    vector<int> l(k), r(k), best(k);
    h.assign(n, 0);
    vector<int> disl(n), disr(n);
    int ans=0;
    for (int i=0; i<k; i++) {
        for (auto v : cmp[i]) {
            h[v] = 0;
        }
        dfs(cmp[i][0]);
        l[i] = cmp[i][0];
        for (auto v : cmp[i]) {
            if (h[v] > h[l[i]]) {
                l[i] = v;
            }
        }
        for (auto v : cmp[i]) {
            h[v] = 0;
        }
        dfs(l[i]);
        r[i] = cmp[i][0];
        for (auto v : cmp[i]) {
            if (h[r[i]] < h[v]) {
                r[i] = v;
            }
        }
        for (auto v : cmp[i]) {
            disl[v] = h[v];
            h[v] = 0;
        }
        dfs(r[i]);
        for (auto v : cmp[i]) {
            disr[v] = h[v];
            h[v] = 0;
        }
        ans = max(ans, disl[r[i]]);
        best[i] = cmp[i][0];
        for (auto v : cmp[i]) {
            int val = max(disl[best[i]], disr[best[i]]);
            //if (i==1) cout << best[i] << " " << val << " " << v << " " << max(disl[v], disr[v]) << endl;
            if (val > max(disl[v], disr[v])) {
                best[i] = v;
            }
        }
    }
    vector<int> vals;
    for (int i=0; i<k; i++) {
        int v = best[i];
        int val = max(disl[v], disr[v]);
        vals.push_back(val);
    }
    sort(vals.begin(), vals.end(), greater<int>());
    int tmx=0, tsmx=0;
    for (int i=0; i<k; i++) {
        if (i<2) tmx += vals[i];
        if (i>0 && i<3) tsmx+=vals[i];
    }
    if (k==1) {
        return ans;
    }
    return max({
        ans, tmx+L, tsmx+2*L
    });
}
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