Submission #928220

#	Time	Username	Problem	Language	Result	Execution time	Memory
928220		vjudge1	Amusement Park (CEOI19_amusementpark)	C++17	19 / 100	54 ms	456 KiB

amusementpark

#include<bits/stdc++.h>

using namespace std;

#define F first
#define S second
#define ll long long
#define maksim gay
#define int ll
#define pb push_back
#define sz(s) (int)s.size()
#define pii pair<int,int>
#define all(v) v.begin(),v.end()
#define mem(a,i) memset(a,i,sizeof(a))
#define in insert
#define lb lower_bound
#define ub upper_bound

const int MAX=20;
const int inf=1e10;
const int N=2e5;

int n,m;
int a[MAX],b[MAX];
int use[MAX];
bool ok;
vector<int> g[MAX];

void dfs(int v){
  use[v]=1;
  for(auto to:g[v]){
    if(use[to]==1){
      ok=0;
    }
    else if(!use[to])dfs(to);
  }
  use[v]=2;
}

void solve(){
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>a[i]>>b[i];
  }
  int ans=0;
  for(int i=0;i<(1<<m);i++){
    for(int i=1;i<=n;i++){
      g[i].clear();
      use[i]=0;
    }
    ok=1;
    int cost=0;
    for(int j=0;j<m;j++){
      if((i>>j)&1){
        cost++;
        swap(a[j],b[j]);
      }
      g[a[j]].pb(b[j]);
      if((i>>j)&1){
        swap(a[j],b[j]);
      }
    }
    for(int i=1;i<=n;i++){
      if(!use[i])dfs(i);
    }
    if(ok)ans+=cost;
  }
  cout<<ans<<"\n";
}


main(){
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t=1;
  // cin>>t;
  while(t--){
    solve();
  }
}

Compilation message (stderr)

amusementpark.cpp:72:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   72 | main(){
      | ^~~~

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 0 / 23
• Subtask 4: 0 / 21
• Subtask 5: 0 / 37