Submission #945621

#	Time	Username	Problem	Language	Result	Execution time	Memory
945621		vjudge1	Amusement Park (CEOI19_amusementpark)	C++17	19 / 100	3064 ms	3672 KiB

amusementpark

#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
 
#define ff first
#define ss second
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define int long long
#define rnd(l, r) uniform_int_distribution<int>(l, r)(rng)
 
using namespace std;
 
void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);} 
int pow(int a,int b,int m){int ans=1;while(b){if(b&1){ans=(ans*a)%m;}b>>=1;a=(a*a)%m;}return ans;}
int binpow(int a,int b){int ans=1;while(b){if(b&1){ans=(ans*a);}b>>=1;a=(a*a);}return ans;}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
const int N = 1e5 + 100, mxc = 105, inf = 1e18, MX = 1e5 + 10;

vector <int> g[N];
int vis[N];

bool f = 0;
void dfs(int v){
	if(f)return;
	vis[v] = 1;
	for(auto to : g[v]){
		if(vis[to] == 1){
			f = 1;
			return;
		}
		dfs(to);
	}
	vis[v] = 2;
}

main(){
	iostream::sync_with_stdio(false);	
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, m;
    cin >> n >> m;
    vector <pair <int,int> > vp;
    for(int i=  1; i <= m; i++){
		int a, b;
		cin >> a >> b;
		vp.pb({a, b});
	}
	int ans = 0;
	for(int bit = 0; bit < (1 << m); bit++){
		
		for(int i = 0; i < m; i++){
			if(bit & (1 << i)){
				g[vp[i].ss].pb(vp[i].ff);
			}else{
				g[vp[i].ff].pb(vp[i].ss);
			}
		}
		f = 0;
		for(int i = 1; i <= n; i++){
			if(vis[i] == 0)
				dfs(i);
		}
		for(int i = 1; i <= n; i++){
			if(!f){
				for(auto to : g[i]){
					ans +=(to < i);
				}
			}
			g[i].clear();
			vis[i] = 0;
		}
	}
	cout << ans;
}
/*
 * Before implementing the problem:
	
	Do I understand the problem correctly?
	Which places are tricky? What do I need to remember to implement them correctly?
	Which place is the heaviest by implementation? Can I do it simpler?
	Which place is the slowest? Where do I need to be careful about constant factors and where I can choose slower but simpler implementation?
	----------------------------------
	If not AC:
 
	Did you remember to do everything to handle the tricky places you thought about before?
	Is the solution correct?
	Do I understand the problem correctly?
	----------------------------------
	If you have a test on which the solution gives wrong answer:
 
	Is the solution doing what it was supposed to do?
	Is the problem in the code or in the idea?
*/

Compilation message (stderr)

amusementpark.cpp:39:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   39 | main(){
      | ^~~~
amusementpark.cpp: In function 'void fp(std::string)':
amusementpark.cpp:15:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 | void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
amusementpark.cpp:15:70: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 | void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                                                               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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