Submission #1010087

#	Time	Username	Problem	Language	Result	Execution time	Memory
1010087		SG2Alok	Commuter Pass (JOI18_commuter_pass)	C++17	0 / 100	62 ms	17744 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n'
#define hitaf ios_base::sync_with_stdio(false); cin.tie(NULL);
#define fi first
#define se second
 
const ll MOD = 998244353;
const ll INF = 4500000000000000000LL;
 
// dp[i][0] = par -> child, dp[i][1] = child -> par
 
int n, m, s, t, u, V;
ll dp[100005][2];
vector<pair<int, int>> adj[100005];
vector<int> p[100005], child[100005];
ll distV[100005], distU[100005], dist[100005];
bool vis[100005];

void dijkstra(ll start, ll dist[100005]){
    for(int i = 1; i <= n; i++) dist[i] = 0;
    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq;
    pq.push({0, start});
    dist[start] = 0;
    while(!pq.empty()){
        auto now = pq.top();
        pq.pop();
        
        if(dist[now.se] < now.fi) continue;
        for(auto v: adj[now.se]){
            if(dist[v.fi] < now.fi + v.se) continue;
            dist[v.fi] = now.fi + v.se;
            pq.push({dist[v.fi], v.fi});
        }
    } 
}
 
ll dfs1(ll u){
    if(dp[u][0] != -1) return dp[u][0];
    
    dp[u][0] = distV[u];
    for(auto v: p[u]){
        dp[u][0] = min(dp[u][0], dfs1(v));
    }
    
    return dp[u][0];
}
 
ll dfs2(ll u){
    if(dp[u][1] != -1) return dp[u][1];
    
    dp[u][1] = distV[u];
    for(auto v: child[u]){
        dp[u][1] = min(dp[u][1], dfs2(v));
    }
    
    return dp[u][1];
}
 
int main(){
    hitaf
    cin >> n >> m;
    cin >> s >> t;
    cin >> u >> V;
    
    for(int i = 1; i <= m; i++){
        int x, y, w;
        cin >> x >> y >> w;
        adj[x].push_back({y, w});
        adj[y].push_back({x,w});
    }
        
    dijkstra(s, dist);
    dijkstra(u, distU);
    dijkstra(V, distV);
    
    queue<int> q;
    q.push(t);
    vis[t] = true;
    while(!q.empty()){
        ll now = q.front();
        q.pop();
        for(auto v: adj[now]){
            if(dist[v.fi] + v.se == dist[now]){
                p[now].push_back(v.fi);
                child[v.fi].push_back(now);
                if(vis[v.fi]) continue;
                vis[v.fi] = true;
                q.push(v.fi);
            }
        }
    }
    
    for(int i = 1; i <= n; i++){
        dp[i][1] = -1;
        dp[i][0] = -1;
    }
    
    ll ans = distU[V];
    
    for(int i = 1; i <= n; i++){
        if(!p[i].empty() || !child[i].empty()){
            ans = min(ans, distU[i] + min(dfs1(i), dfs2(i)));
        }
    }
    
    //for(auto x: child[7]) cout << x << " ";
    //cout << endl;
    cout << ans << endl;
    return 0;
}
    
 
/*
    7 1 2 9 0
*/

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