Submission #636915

#TimeUsernameProblemLanguageResultExecution timeMemory
636915chjiaoCommuter Pass (JOI18_commuter_pass)C++17
0 / 100
380 ms44592 KiB
#include <bits/stdc++.h>
using namespace std;
#define ll  long long
#define newl '\n'
const int mod = 1e9+7;
const ll MAX = 0x3f3f3f3f3f3f3f3f;
const int mn = 1e5+1;
vector<vector<pair<ll,ll>>> neighbors(mn);
vector<ll> du(mn,LLONG_MAX/2);
vector<ll> dv(mn,LLONG_MAX/2);
vector<ll> ds(mn,LLONG_MAX/2);
vector<ll> dpu(mn,LLONG_MAX/2);
vector<ll> dpv(mn,LLONG_MAX/2);

bool vis[mn];
ll ans;
 
void dijkstra(ll s, vector<ll> &d) { // Source and destination
	fill(vis, vis + 100001, false);  //初始化visited为false

	priority_queue<pair<ll, ll>> pq;
	pq.push({0, s});
	while (!pq.empty()) {
		ll c, node;
		tie(c, node) = pq.top();  //c: 从 start 到 node 的cost
		pq.pop();

		if (!vis[node]) {
			d[node] = -c;   //距离
			vis[node] = true;
			for (auto& i : neighbors[node]) pq.push({c - i.second, i.first});
		}
	}

    // fill(vis, vis + mn, false);
	// using T = pair<ll,ll>; priority_queue<T,vector<T>,greater<T>> pq;
	// d[s] = 0; // The shortest path from a node to itself is 0
	// pq.push({0, s});
 
	// while (!pq.empty()) {
    //     ll pos, cost;
	// 	tie(pos, cost) = pq.top();
    //     pq.pop();
    //     if(vis[pos]==true){
    //         continue;
    //     }
       
    //     if(!vis[pos]) {
    //          vis[pos] = true;
    //          d[pos] = cost;
    //          for (auto & [place, value]: neighbors[pos]) {
    //             pq.push({cost+value, place});
    //          } 

    //     }
	// 	// for (auto & [place, value]: neighbors[pos]) {
	// 	// 	// If we can reach a neighbouring node faster,
	// 	// 	// we update its minimum distance
	// 	// 	if (d[pos]+value < d[place]) {
    //     //         d[place] = d[pos]+value;
	// 	// 		pq.push({d[place], place});
	// 	// 	}
	// 	// }
	// }
}
void dijkstra2(ll start, ll end) { // Source and destination
    fill(vis,vis+mn , false);
    fill(dpu.begin(),dpu.end(),LLONG_MAX/2);
    fill(dpv.begin(), dpu.end(), LLONG_MAX/2);
 
	priority_queue<pair<ll,pair<ll, ll>>> pq;
	pq.push({0, {start,0}});
    dpu[0]= LLONG_MAX/2;
    dpv[0] = LLONG_MAX/2;
 
	while (pq.size()) {
        ll cost, curr, last;
		cost = pq.top().first;
        curr = pq.top().second.first;
        last = pq.top().second.second;
        pq.pop();
		if(vis[curr]!=true){
            vis[curr] = true;
			ds[curr] = -cost;
			dpu[curr] = min(dpu[last], du[curr]);
			dpv[curr] = min(dpv[last], dv[curr]);
			for (auto [place, value] : neighbors[curr]) {
				// If we can reach a neighbouring node faster,
				// we update its minimum distance
				if(ds[place]> ds[curr]+value){
					pq.push({-cost-value,{place, curr}});
				}
			}
        }else if (-cost == ds[curr] ) { 
            if(min(dpu[last], du[curr]) + min(dpv[last], dv[curr]) < dpu[curr]+dpv[curr]){
                dpu[curr] = min(dpu[last], du[curr]);
            	dpv[curr] = min(dpv[last], dv[curr]);
            }
 
        }
	}
    ans = min(ans, dpu[end]+dpv[end]);
}
 
int main(){
    ios_base::sync_with_stdio(false); cin.tie(0);
    // freopen("CommuterPass.in", "r", stdin);
    //freopen("nocross.out", "w", stdout); 
    ll N,M,S,T,U,V,a,b,c;
    cin >> N >> M;
    cin >> S >> T >> U >> V;//s,t is free, U,V needs minimizing
	// S--;T--;U--;V--;
    for(int i=0; i<M; i++){
        cin >> a >> b >> c;
        // a--;
        // b--;
        neighbors[a].push_back(make_pair(b,c));
        neighbors[b].push_back(make_pair(a,c));
 
    }
 
    dijkstra(U, du);
    dijkstra(V, dv);
    ans = du[V];
    dijkstra2(S,T);
    dijkstra2(T,S);
    cout << ans << endl;
 
 
}
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