Submission #996193

#	Time	Username	Problem	Language	Result	Execution time	Memory
996193		54skyxenon	Crocodile's Underground City (IOI11_crocodile)	C++17	100 / 100	1786 ms	140084 KiB

crocodile

// https://oj.uz/problem/view/IOI11_crocodile

/** Needed for linking!!! */
#include "crocodile.h"

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define INF (ll)1e18

int travel_plan(int N, int M, int R[][2], int L[], int K, int P[]) {
    vector<map<int, int>> graph(N);
    vector<set<int>> visited(N);

    for (int i = 0; i < M; i++) {
        int u = R[i][0];
        int v = R[i][1];
        graph[u][v] = graph[v][u] = L[i];
    }

    // Run Dijkstra's and only care about the second best distance, propagated downwards
    vector<vector<ll>> dist(graph.size(), {INF, INF});
    priority_queue<pair<ll, ll>> pq;

    for (int i = 0; i < K; i++) {
        pq.push({0, P[i]});
        dist[P[i]][0] = dist[P[i]][1] = 0;
    }

    while (pq.size()) {
        auto [d, u] = pq.top();
        pq.pop();
        d = -d;

        if (d > dist[u][1]) {
            continue;
        }

        // Thank you to Sreepranad Devarakonda from USACO Guide
        for (auto& [v, w] : graph[u]) {
            ll cost = w + d;

            // ! We only add to the priority queue (for a downstream effect) when we set the 2nd shortest distance
            if (cost < dist[v][0]) {
                // The first shortest distance can become the 2nd shortest distance
                if (dist[v][0] != dist[v][1] && dist[v][0] < INF) {
                    dist[v][1] = dist[v][0];
                    pq.push({-dist[v][1], v});
                }
                dist[v][0] = cost;
            }
            else if (cost < dist[v][1]) {
                dist[v][1] = cost;
                pq.push({-cost, v});
            }
        }
    }

    return dist[0][1];
}

• Subtask 1: 46 / 46
• Subtask 2: 43 / 43
• Subtask 3: 11 / 11