Submission #702575

#	Time	Username	Problem	Language	Result	Execution time	Memory
702575		1075508020060209tc	Olympic Bus (JOI20_ho_t4)	C++14	0 / 100	62 ms	13044 KiB

ho_t4

//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define X first
#define Y second

int n;int m;
struct edg{
int x;int y;int d;
}es[50005];
vector<int>e[200005];
vector<int>er[200005];

int vis[200005];
int sccid;
int scc[200005];
vector<int>dfn;

void dfs1(int nw){
vis[nw]=1;
for(int i=0;i<e[nw].size();i++){
    int id=e[nw][i];
    int v=es[id].y;
    if(vis[v]){continue;}
    dfs1(v);
}
dfn.push_back(nw);
}

void dfs2(int nw){
scc[nw]=sccid;
for(int i=0;i<e[nw].size();i++){
    int id=e[nw][i];
    int v=es[id].x;
    if(scc[v]){continue;}
    dfs2(v);
}
}

void kosaraju(){

for(int i=1;i<=n;i++){
    if(!vis[i]){
        dfs1(i);
    }
}
sccid=1;
reverse(dfn.begin(),dfn.end());
for(int i=0;i<dfn.size();i++){
    int v=dfn[i];
    if(scc[v]){continue;}
    sccid++;
    dfs2(v);
}


}

int ch[500005];
void dfs(int nw){
    ch[nw]=1;
    for(int i=0;i<e[nw].size();i++){
        int id=e[nw][i];
        int v=es[id].y;
        if(ch[v]){continue;}
        dfs(v);
    }
}


signed main(){
cin>>n>>m;
for(int i=1;i<=m;i++){
    int a;int b;int c;int d;
    cin>>a>>b>>c>>d;
    e[a].push_back(i);
    e[b].push_back(i);
    es[i]={a,b,d};
}
kosaraju();

if(scc[1]==scc[n]){
    cout<<0;return 0;
}

dfs(1);

if(ch[n]){
    int ans=1e16;int cnt=0;
    for(int i=1;i<=m;i++){
        int a=scc[es[i].x];int b=scc[es[i].y];int d=es[i].d;

        if(a==scc[1]&&b==scc[n]){
            ans=min(ans,d);cnt++;
            continue;
        }
        if(ch[a]&&b==scc[n]){
            cnt++;
        }
    }
if(cnt<=1){ans=1e16;}

if(ans>=1e16){
    cout<<-1;
}else{
    cout<<ans;
}


return 0;
}
for(int i=1;i<=n;i++){
    ch[i]=0;
}
dfs(n);
if(ch[1]){
    int ans=1e16;int cnt=0;
    for(int i=1;i<=m;i++){
        int a=scc[es[i].x];int b=scc[es[i].y];int d=es[i].d;

        if(a==scc[n]&&b==scc[1]){
            ans=min(ans,d);cnt++;
            continue;
        }
        if(ch[a]&&b==scc[1]){
            cnt++;
        }
    }
if(cnt<=1){ans=1e16;}

if(ans>=1e16){
    cout<<-1;
}else{
    cout<<ans;
}


return 0;
}
cout<<-1;return 0;


}

Compilation message (stderr)

ho_t4.cpp: In function 'void dfs1(long long int)':
ho_t4.cpp:22:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
ho_t4.cpp: In function 'void dfs2(long long int)':
ho_t4.cpp:33:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
ho_t4.cpp: In function 'void kosaraju()':
ho_t4.cpp:50:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 | for(int i=0;i<dfn.size();i++){
      |             ~^~~~~~~~~~~
ho_t4.cpp: In function 'void dfs(long long int)':
ho_t4.cpp:63:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |     for(int i=0;i<e[nw].size();i++){
      |                 ~^~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63