Submission #976548

#	Time	Username	Problem	Language	Result	Execution time	Memory
976548		Haanhtien	Relay Marathon (NOI20_relaymarathon)	C++14	17 / 100	178 ms	68872 KiB

RelayMarathon

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

#define ll long long
#define ii pair<ll, ll>
#define fi first
#define se second

struct datax{
    ll u, v, w;
};

ll n, m, k, cities[100005], ans, t, u, v, w, dist[100005], h[100005], a, b, spe[100005];
ll flat[100005];

vector<ii> adj[100005];
datax queries[400005];

ii dijkstra(ll s){
    priority_queue<ii, vector<ii>, greater<ii>> pq;
    for(int i=1; i<=n; i++) dist[i] = 1e9;
   	dist[s]=0;
	pq.push({0, s});
    while(!pq.empty()){
        ll val = pq.top().fi;
        ll u = pq.top().se;
        pq.pop();
        if(dist[u]!=val) continue;
		if(spe[u]){
			return {dist[u], u};
		}
        for(auto edge:adj[u]){
            ll v = edge.fi;
            ll w = edge.se;
            
            if(dist[v]>dist[u]+w){
                dist[v] = dist[u]+w;
                pq.push({dist[v], v});
            }

        }
    }
	return {1e9, 0};
}

void dijkstra2(){
    priority_queue<ii, vector<ii>, greater<ii>> pq;
    for(int i=1; i<=n; i++) dist[i] = 1e9;
    for(int i=1; i<=n; i++){
		if(!spe[i]) continue;
       	dist[i]=0;
       	pq.push({0, i});
      	h[i] = i;
    }
    while(!pq.empty()){
        ll val = pq.top().fi;
        ll u = pq.top().se;
        pq.pop();
        if(dist[u]!=val) continue;
        for(auto edge:adj[u]){
            ll v = edge.fi;
            ll w = edge.se;
            if(dist[v]==dist[u]+w) flat[v] = 1;
            if(dist[v]>dist[u]+w){
                dist[v] = dist[u]+w;
                h[v] = h[u];
                flat[v]=0;
                pq.push({dist[v], v});
            }

        }
    }
}
void inp(){
    cin >> n >> m >> k;
    for(int i=1; i<=m; i++){
        cin >> u >> v >> w;
        queries[i] = {u, v, w};
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
    }
    for(int i=1; i<=k; i++){
		cin >> cities[i];
		spe[cities[i]]=1;
	}
}

pair<ll, ii> choose(){
	ll ans=LLONG_MAX, a=0, b=0;
   	for(int i=1; i<=m; i++){
       ll u = queries[i].u, v = queries[i].v, w = queries[i].w;
       if(flat[u]||flat[v]||h[u]!=h[v]){
          	ll t = dist[u] + dist[v] + w;
			if(t<ans){
				ans = t;
				a = h[u];
				b = h[v];
			}
            //cout << dist[u] << ' '  << dist[v] << '\n';
            //cout << flat[u] << ' ' <<flat[v] << '\n';
       }
    }
	return {ans, {a, b}};

} 


ll nearest(ll a, ll b){
	ii tmp1 = dijkstra(a);
	ll c = tmp1.se;
	ll t3 = tmp1.fi;
	spe[c]=0;
	ii tmp2 = dijkstra(b);
	ll d = tmp2.se;
	ll t4 = tmp2.fi;
	spe[c]=1;
	return t3+t4;
}
void solve(){
   	dijkstra2();
	pair<ll, ii> tmp = choose();
   	ll t1 = tmp.fi;
	ll a = tmp.se.fi;
	ll b = tmp.se.se;
	spe[a]=0, spe[b]=0;
	dijkstra2();
	ll t2 = choose().fi;
	ll ans = t1+t2; 
	ans = min({ans, nearest(a, b), nearest(b, a)});
	
	cout << ans;
	  
   	
	
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    //freopen("cities.inp", "r", stdin);
    //freopen("cities.out", "w", stdout);
    inp();
    solve();
    return 0;
}

Compilation message (stderr)

RelayMarathon.cpp: In function 'long long int nearest(long long int, long long int)':
RelayMarathon.cpp:114:5: warning: unused variable 'd' [-Wunused-variable]
  114 |  ll d = tmp2.se;
      |     ^

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 0 / 25
• Subtask 4: 0 / 58