Submission #1069897

#	Time	Username	Problem	Language	Result	Execution time	Memory
1069897		Hugo1729	Commuter Pass (JOI18_commuter_pass)	C++17	16 / 100	320 ms	21684 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<pair<ll,ll>> adj[100001];

ll n, m;

vector<ll> dijkstra(ll start){
    vector<ll> dist(n+1, LLONG_MAX);

	// Dijkstra's algorithm
	using T = pair<long long, ll>;
	priority_queue<T, vector<T>, greater<T>> pq;

	dist[start] = 0;  // The shortest path from a node to itself is 0
	pq.push({0, start});

	while (!pq.empty()) {
		const auto [cdist, node] = pq.top();
		pq.pop();
		if (cdist != dist[node]) { continue; }
		for (const pair<ll, ll> &i : adj[node]) {
			// If we can reach a neighbouring node faster,
			// we update its minimum distance
			if (cdist + i.first < dist[i.second]) {
				pq.push({dist[i.second] = cdist + i.first, i.second});
			}
		}
	}

    return dist;
}

ll solve(ll a, ll b, ll c, ll d){
    
    vector<ll> path1 = dijkstra(a),path2 = dijkstra(b),sus1=dijkstra(c),sus2=dijkstra(d);

    vector<ll> dp(n+1,LLONG_MAX/4),dp1(n+1,LLONG_MAX/4),dp2(n+1,LLONG_MAX/4);
    // vector<pair<ll,ll>> dp1(n+1,{LLONG_MAX,LLONG_MAX}),dp2(n+1,{LLONG_MAX,LLONG_MAX});

    vector<pair<ll,ll>> elza;

    for(ll i=1;i<=n;i++){
        if(path1[i]+path2[i]==path1[b])elza.push_back({path1[i],i});
    }

    dp[a]=sus1[a]+sus2[a];
    dp1[a]=sus1[a];
    dp2[a]=sus2[a];

    sort(elza.begin(),elza.end());

    for(ll i=0;i<elza.size();i++){
        ll v = elza[i].second;
        for(auto [cost, w] : adj[v]){
            if(path1[v]+path2[v]==path1[b]&&path1[w]<path1[v]){
                dp1[v]=min(dp1[w],sus1[v]);
                dp2[v]=min(dp2[w],sus2[v]);
                dp[v]=min(dp[v],dp[w]);
            }
        }

        for(auto [cost, w] : adj[v]){
            if(path1[v]+path2[v]==path1[b]&&path1[w]<path1[v]){
                dp[v]=min(dp[v],dp1[v]+sus2[v]);
                dp[v]=min(dp[v],dp2[v]+sus1[v]);
            }
        }
        // cout << v <<' ' << path1[v] <<  ": " << dp[v] << ' ' << dp1[v] << ' ' << dp2[v] << '\n';
    }

    return min(dp[b],sus1[d]);
}

int main(){
    cin.tie(0)->sync_with_stdio(0);

    ll a,b,c,d;


    cin >> n >> m >> a >> b >> c >> d;

    for(ll i=0;i<m;i++){
        ll x,y,cost; cin >> x >> y >> cost;
        adj[x].push_back({cost,y});
        adj[y].push_back({cost,x});
    }


    cout << min(solve(a,b,c,d),solve(b,a,c,d));

    // cout << '\n';

    // for(ll i = 0;i<elza.size();i++)cout << elza[i].first << ' ' << elza[i].second << '\n';


    // cout << '\n';

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'll solve(ll, ll, ll, ll)':
commuter_pass.cpp:53:17: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |     for(ll i=0;i<elza.size();i++){
      |                ~^~~~~~~~~~~~

• Subtask 1: 16 / 16
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45