Submission #1025926

#	Time	Username	Problem	Language	Result	Execution time	Memory
1025926		onbert	Dreaming (IOI13_dreaming)	C++17	100 / 100	67 ms	14812 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5, INF = 1e9;
int n, m, l;
vector<pair<int,int>> adj[maxn];
int dist[maxn];
vector<int> cur;

void dfs(int u) {
    cur.push_back(u);
    for (auto [v, w]:adj[u]) if (dist[v] == -1) {
        dist[v] = dist[u] + w;
        dfs(v);
    }
}

int finish;
vector<int> track;
bool done;
void dfs2(int u) {
    if (!done) track.push_back(u);
    if (u==finish) done = true;
    for (auto [v, w]:adj[u]) if (dist[v] == -1) {
        dist[v] = dist[u] + w;
        dfs2(v);
    }
    if (!done) track.pop_back();
}

int32_t travelTime(int32_t N, int32_t M, int32_t L, int32_t A[], int32_t B[], int32_t T[]) {
    n = N, m = M, l = L;
    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++) dist[i] = -1;
    int32_t ans1 = 0;
    vector<int> vals;
    for (int i=0;i<n;i++) if (dist[i] == -1) {
        cur.clear();
        dist[i] = 0;
        dfs(i);
        int start = i;
        for (int j:cur) if (dist[j] > dist[start]) start = j;
        for (int j:cur) dist[j] = -1;
        cur.clear();
        dist[start] = 0;
        dfs(start);
        finish = start;
        for (int j:cur) if (dist[j] > dist[finish]) finish = j;
        ans1 = max(dist[finish], ans1);
        for (int j:cur) dist[j] = -1;
        dist[start] = 0, done = false;
        track.clear();
        dfs2(start);
        int cost = INF;
        for (int j:track) cost = min(max(dist[finish]-dist[j], dist[j]), cost);
        vals.push_back(cost);
    }
    sort(vals.rbegin(), vals.rend());
    int ans2 = 0, ans3 = 0;
    if (vals.size() >= 2) ans2 = l + vals[0] + vals[1];
    if (vals.size() >= 3) ans3 = l + l + vals[1] + vals[2];
    return max({ans1, ans2, ans3});
}

// signed main() {
//     ios::sync_with_stdio(0); cin.tie(0);
//     int32_t n, m, l;
//     cin >> n >> m >> l;
//     int32_t a[m], b[m], t[m];
//     for (int i=0;i<m;i++) cin >> a[i] >> b[i] >> t[i];
//     cout << travelTime(n, m, l, a, b, t) << endl;
// }

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