Submission #209308

#	Time	Username	Problem	Language	Result	Execution time	Memory
209308		AQT	Olympic Bus (JOI20_ho_t4)	C++14	0 / 100	40 ms	1944 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

int N, M;
vector<int> graph[205]; 
vector<int> rgraph[205];
int u[50005], v[50005], p[2][50005];
bool used[50005];
long long dist[2][205], cst[50005], rev[50005], rdist[2][205];
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;

void dijkstra(int s, int t){
	for(int i = 1; i<=N; i++){
		dist[t][i] = LLONG_MAX>>4;
	}
	dist[t][s] = 0;
	pq.push({0, s});
	while(pq.size()){
		auto pii = pq.top();
		pq.pop();
		if(dist[t][pii.second] != pii.first){
			continue;
		}
		int n = pii.second;
		for(int e : graph[n]){
			if(u[e] == n && dist[t][v[e]] > dist[t][u[e]] + cst[e]){
				dist[t][v[e]] = dist[t][u[e]] + cst[e];
				p[t][v[e]] = e;
				pq.push({dist[t][v[e]], v[e]});
			}
		}
	}
}

void rdijkstra(int s, int t){
	for(int i = 1; i<=N; i++){
		rdist[t][i] = LLONG_MAX>>4;
	}
	rdist[t][s] = 0;
	pq.push({0, s});
	while(pq.size()){
		auto pii = pq.top();
		pq.pop();
		if(rdist[t][pii.second] != pii.first){
			continue;
		}
		int n = pii.second;
		for(int e : rgraph[n]){
			if(v[e] == n && rdist[t][u[e]] > rdist[t][v[e]] + cst[e]){
				rdist[t][u[e]] = rdist[t][v[e]] + cst[e];
				//p[t][u[e]] = u[e];
				pq.push({rdist[t][u[e]], u[e]});
			}
		}
	}
}

int main(){
	cin.sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> N >> M;
	for(int i = 1; i<=M; i++){
		cin >> u[i] >> v[i] >> cst[i] >> rev[i];
		graph[u[i]].push_back(i);
	}
	dijkstra(1, 0);
	dijkstra(N, 1);
	rdijkstra(1, 0);
	rdijkstra(N, 1);
	long long ans = dist[0][N] + dist[1][1];
	int crnt = N;
	while(p[0][crnt] && crnt != 1){
		used[p[0][crnt]] = 1;
		crnt = u[p[0][crnt]];
	}
	crnt = 1;
	while(p[1][crnt] && crnt != N){
		used[p[1][crnt]] = 1;
		crnt = u[p[1][crnt]];
	}
	for(int e = 1; e<=M; e++){
		if(!used[e]){
			ans = min(ans, dist[0][N] + dist[1][v[e]] + rdist[0][u[e]] + cst[e] + rev[e]);
			ans = min(ans, dist[1][1] + dist[0][v[e]] + rdist[1][u[e]] + cst[e] + rev[e]);		
		}
	}
	for(int e = 1; e<=M; e++){
		if(used[e]){
			swap(u[e], v[e]);
			graph[u[e]].push_back(e);
			dijkstra(1, 0);
			dijkstra(N, 1);
			graph[u[e]].pop_back();
			swap(u[e], v[e]);
			ans = min(ans, dist[0][N] + dist[1][1] + rev[e]);
		}
	}
	if(ans >= LLONG_MAX>>4){
		ans = -1;
	}
	cout << ans;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63