Submission #865764

#	Time	Username	Problem	Language	Result	Execution time	Memory
865764		Requiem	Commuter Pass (JOI18_commuter_pass)	C++17	31 / 100	254 ms	29700 KiB

commuter_pass

#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define MOD 1000000007
#define INF 1e18
#define fi first
#define se second
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define sz(a) ((int)(a).size())
#define endl '\n'
#define pi 3.14159265359
#define TASKNAME "bus"
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
using namespace std;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
const int MAXN = 2e5 + 9;
int n,m,s,t,u,v,dist1[MAXN],dist2[MAXN];
vector<ii> g[MAXN];
void prep(){
    priority_queue<ii,vector<ii>,greater<ii>> pq;
    pq.push({0,s});
    memset(dist1,0x3f,sizeof(dist1));
    dist1[s] = 0;
    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
        pq.pop();
        if (du > dist1[u]) continue;
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            if (dist1[v] > dist1[u] + w){
                dist1[v] = dist1[u] + w;
                pq.push({dist1[v],v});
            }
        }
    }
    memset(dist2,0x3f,sizeof(dist2));
    dist2[t] = 0;
    pq.push({0,t});
    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
        pq.pop();
        if (du > dist2[u]) continue;
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            if (dist2[v] > dist2[u] + w){
                dist2[v] = dist2[u] + w;
                pq.push({dist2[v],v});
            }
        }
    }
}
int dist[MAXN];
ii best[MAXN];
void upd(ii &a,ii u){
    if (dist[a.se] > dist[u.se]) a = u;
}
bool onpath(int u,int v,int w){
    return (dist1[u] + dist2[v] + w == dist1[t] or dist1[v] + dist2[u] + w == dist1[t]);
}
void dijk(int s){
    priority_queue<ii,vector<ii>,greater<ii>> pq;
    pq.push({0,s});
    memset(dist,0x3f,sizeof(dist));
    dist[s] = 0;
    best[s] = {0,s};

    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
        pq.pop();
        if (du > dist[u]) continue;
//        cout<<u<<' '<<du<<' '<<best[u].fi<<' '<<best[u].se<<endl;
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            int dx = best[u].fi; //khoang k den k1
            int mx = best[u].se; //mx la dinh bat dau
//            if (onpath(u,v,w)) cout<<u<<' '<<v<<' '<<w<<endl;
            if (onpath(u,v,w) and onpath(best[u].se,v,best[u].fi + w)){
                if (dist[v] > dist[best[u].se]){
                    dist[v] = dist[best[u].se];
                    pq.push({dist[v],v});
                    best[v] = {best[u].fi + w,best[u].se};
                }
            }
            if (dist[v] > dist[u] + w){
                dist[v] = dist[u] + w;
                best[v] = {0,v};
                pq.push({dist[v],v});
            }
        }
    }
    cout<<dist[v]<<endl;
}
main()
{
    fast;
  //  freopen(TASKNAME".inp","r",stdin);
  //  freopen(TASKNAME".out","w",stdout);
    cin>>n>>m;
    cin>>s>>t;
    cin>>u>>v;
    for(int i=1;i<=m;i++){
        int u,v,w;
        cin>>u>>v>>w;
        g[u].pb({v,w});
        g[v].pb({u,w});
    }
    prep();
    dijk(u);



}

Compilation message (stderr)

commuter_pass.cpp: In function 'void dijk(long long int)':
commuter_pass.cpp:85:17: warning: unused variable 'dx' [-Wunused-variable]
   85 |             int dx = best[u].fi; //khoang k den k1
      |                 ^~
commuter_pass.cpp:86:17: warning: unused variable 'mx' [-Wunused-variable]
   86 |             int mx = best[u].se; //mx la dinh bat dau
      |                 ^~
commuter_pass.cpp: At global scope:
commuter_pass.cpp:104:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  104 | main()
      | ^~~~

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