Submission #746063

#	Time	Username	Problem	Language	Result	Execution time	Memory
746063		vjudge1	Cities (BOI16_cities)	C++17	0 / 100	3 ms	980 KiB

cities

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

#define int long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define fi first
#define se second

struct edge {
    int from, to, wei;
    bool operator < (const edge &other) const {
        return wei > other.wei;
    }
};

const int maxn = 1000;
const int inf = 1e16 + 42;

int n, k, m;
vector<edge> graph[1 + maxn];
bool special[1 + maxn];
vector<int> specials;

void dijkstra(int source, vector<int> &dist, vector<int> &path) {
    dist.assign(1 + n, -1);
    path.assign(1 + n, -1);
   // dist[source] = 0;
    priority_queue<edge> q;
    q.push({0, source, 0});
    while(!q.empty()) {
        edge cur = q.top();
        q.pop();
        if(dist[cur.to] != -1) {
            continue;
        }
        dist[cur.to] = cur.wei;
        path[cur.to] = cur.from;
        for(const edge &nei : graph[cur.to]) {
            if(dist[nei.to] == -1 || dist[nei.to] /*<*/> dist[cur.to] + nei.wei) {
                q.push({cur.to, nei.to, dist[cur.to] + nei.wei});
            }
        }
    }
}

vector<pii > prs = {{0, 1}, {0, 2}, {0, 3}};
vector<pii > opp_prs = {{2, 3}, {1, 3}, {1, 2}};

void solve() {
    cin >> n >> k >> m;
    for(int i = 0; i < k; i++) {
        int x;
        cin >> x;
        special[x] = true;
        specials.pb(x);
    }
    for(int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        graph[a].pb({a, b, c});
        graph[b].pb({b, a, c});
    }
    int ans = inf;
    vector<vector<int> > distances(k);
    vector<vector<int> > path(k);
    for(int i = 1; i < k; i++) {
        dijkstra(specials[i], distances[i], path[i]);
    }
#define dist distances
#define sp specials
    for(int idx = 0; idx < 3; idx++) {
        int a = prs[idx].fi, b = prs[idx].se;
        int c = opp_prs[idx].fi, d = opp_prs[idx].se;
        int cur = 0;
        cur += dist[a][sp[b]];
        int minc = inf, mind = inf;
        int x = sp[b];
        while(x != 0) {
            minc = min(minc, dist[c][x]);
            mind = min(mind, dist[d][x]);
            x = path[a][x];
        }
        cur += minc;
        cur += mind;
        if(ans > cur) {
            ans = cur;
        }
    }
    cout << ans << "\n";
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

• Subtask 1: 0 / 22
• Subtask 2: 0 / 14
• Subtask 3: 0 / 15
• Subtask 4: 0 / 23
• Subtask 5: 0 / 26