Submission #853298

#	Time	Username	Problem	Language	Result	Execution time	Memory
853298		Zero_OP	Commuter Pass (JOI18_commuter_pass)	C++14	31 / 100	188 ms	18880 KiB

commuter_pass

#include<bits/stdc++.h>

using namespace std;

#define range(v) begin(v), end(v)
#define compact(v) v.erase(unique(range(v)), end(v))
#define len(x) (int)(x).size()
#define BIT(x, i) ((x)>>(i)&1)
#define MASK(x) (1LL<<(x))

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

template<class T> bool maximize(T& a, const T& b){ if(a<b) return a=b, true; return false; }
template<class T> bool minimize(T& a, const T& b){ if(a>b) return a=b, true; return false; }

const int N=1e5+5;

struct edge{
  int u, v, w;
} e[N*2];

struct item{
  int v, w, id;
};

int n, m, s, t, U, V;
vector<item> g[N];
bool in_shortest_path[N*2];

vector<ll> dijkstra(int st){
  vector<ll> d(n+1, -1); d[st]=0;
  priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>>> pq;
  pq.push({0, st});
  while(!pq.empty()){
    ll cost; int u;
    tie(cost, u)=pq.top(); pq.pop();
    if(d[u]!=cost) continue;
    for(int i=0; i<g[u].size(); ++i){
      int v=g[u][i].v, w=g[u][i].w;
      if(d[v]==-1 or (d[v]>(d[u]+w))){
        d[v]=d[u]+w;
        pq.push({d[v], v});
      }
    }
  }
  return d;
}

ll modify_dijkstra(int st, int ed){
  vector<ll> d(n+1, -1); d[st]=0;
  priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>>> pq;
  pq.push({0, st});
  while(!pq.empty()){
    ll cost; int u;
    tie(cost, u)=pq.top(); pq.pop();
    if(cost!=d[u]) continue;
    for(int i=0; i<g[u].size(); ++i){
      int v=g[u][i].v, w=(in_shortest_path[g[u][i].id]?0:g[u][i].w);
      if(d[v]==-1 or (d[v]>(d[u]+w))){
        d[v]=d[u]+w;
        pq.push({d[v], v});
      }
    }
  }
  return d[ed];
}

void Zero_OP(){
  cin>>n>>m>>s>>t>>U>>V;
  for(int i=1; i<=m; ++i){
    int u, v, c; cin>>u>>v>>c;
    g[u].push_back({v, c, i});
    g[v].push_back({u, c, i});
    e[i]={u, v, c};
  }


  if(n<=300){
    ll d[n+1][n+1];
    memset(d, 0x3f, sizeof(d));

    for(int i=1; i<=m; ++i){
      minimize(d[e[i].u][e[i].v], (ll)e[i].w);
      minimize(d[e[i].v][e[i].u], (ll)e[i].w);
    }

    for(int k=1; k<=n; ++k){
      for(int i=1; i<=n; ++i){
        for(int j=1; j<=n; ++j){
          minimize(d[i][j], d[i][k]+d[k][j]);
        }
      }
    }

    ll ans=d[U][V];
    for(int i=1; i<=n; ++i){
      for(int j=1; j<=n; ++j){
        if(d[s][i]+d[i][j]+d[j][t]==d[s][t]){
          minimize(ans, min(d[U][i]+d[j][V], d[V][i]+d[j][U]));
        }
      }
    }

    cout<<ans;
  }
  else {
    vector<ll> d_s=dijkstra(s), d_t=dijkstra(t);
    for(int i=1; i<=m; ++i){
      int u=e[i].u, v=e[i].v, w=e[i].w;
      if(d_s[u]+w+d_t[v]==d_s[t] or d_s[v]+w+d_t[u]==d_s[t]){
        in_shortest_path[i]=true;
      }
    }

    cout<<modify_dijkstra(U, V);
  }
}

signed main(){
  ios_base::sync_with_stdio(0);
  cin.tie(NULL); cout.tie(NULL);

  #define task "COMPUTER_PASS"
  if(fopen(task".INP", "r")){
    freopen(task".INP", "r", stdin);
    freopen(task".OUT", "w", stdout);
  }

  int TC=1; //cin>>TC;
  while(TC--) Zero_OP();

  return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'std::vector<long long int> dijkstra(int)':
commuter_pass.cpp:40:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<item>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     for(int i=0; i<g[u].size(); ++i){
      |                  ~^~~~~~~~~~~~
commuter_pass.cpp: In function 'll modify_dijkstra(int, int)':
commuter_pass.cpp:59:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<item>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   59 |     for(int i=0; i<g[u].size(); ++i){
      |                  ~^~~~~~~~~~~~
commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:127:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  127 |     freopen(task".INP", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:128:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  128 |     freopen(task".OUT", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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