Submission #864488

#	Time	Username	Problem	Language	Result	Execution time	Memory
864488		Requiem	Amusement Park (CEOI19_amusementpark)	C++17	19 / 100	3060 ms	600 KiB

amusementpark

#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 998244353
#define INF 1e18
#define fi first
#define se second
#define endl "\n"
#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 pi 3.14159265359
#define TASKNAME "amusepark"
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 = 3e2 + 9;
ii edge[MAXN];
int n,m,ans=0;
int degree[MAXN];
vector<int> g[MAXN];
bool visited[MAXN];
queue<int> q;

bool check(){
    for(int i=1;i<=n;i++){
        degree[i] = 0;
        g[i].clear();
    }
    for(int i=1;i<=m;i++){
        g[edge[i].fi].pb(edge[i].se);
        degree[edge[i].se]++;
        // cout<<edge[i].fi<<' '<<edge[i].se<<endl;
    }
    int cnt = 0;
    // cout<<endl<<endl;
    for(int i=1;i<=n;i++){

        if (degree[i] == 0) q.push(i);
    }
    
    while(!q.empty()){
        int u = q.front();
        cnt++;
        q.pop();
        for(auto v: g[u]){
            degree[v]--;
            if (degree[v] == 0) q.push(v);
        }
    }
    return cnt == n;
}
void backtrack(int pos,int cost){
    if (pos==m+1){
        if (check()){
            ans = (ans + cost)%MOD;
        }
        return;
    }
    swap(edge[pos].fi,edge[pos].se);
    backtrack(pos+1,cost+1);
    swap(edge[pos].fi,edge[pos].se);
    backtrack(pos+1,cost);
}
main() 
{ 
    fast; 
    // freopen(TASKNAME".inp","r",stdin); 
    // freopen(TASKNAME".out","w",stdout); 
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>edge[i].fi>>edge[i].se;
    }
    backtrack(1,0);
    cout<<ans<<endl;



} 

Compilation message (stderr)

amusementpark.cpp:69:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   69 | main()
      | ^~~~

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