Submission #960359

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Source Code Expand

#include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <sstream>
#include <functional>
#include <map>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <deque>
#include <set>
#include <list>
#include <numeric>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> P;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const ll INF = 1LL<<29;
const ll mod = 1e9+7;
#define rep(i,n) for(int (i)=0;(i)<(ll)(n);++(i))
#define repd(i,n,d) for(ll (i)=0;(i)<(ll)(n);(i)+=(d))
#define all(v) (v).begin(), (v).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset((m),(v),sizeof(m))
#define chmin(X,Y) ((X)>(Y)?X=(Y),true:false)
#define chmax(X,Y) ((X)<(Y)?X=(Y),true:false)
#define fst first
#define snd second
#define UNIQUE(x) (x).erase(unique(all(x)),(x).end())
template<class T> ostream &operator<<(ostream &os, const vector<T> &v){int n=v.size();rep(i,n)os<<v[i]<<(i==n-1?"":" ");return os;}

#define N 100000
int n, m;
vector<P> e[N];
int w[N];

void dfs(int u, int d, ll *s, bool &f, ll &es){
	w[u] = d;
	s[d]++;
	es += e[u].size();
	for(P x: e[u]){
		int v = x.fst, d2 = (d+x.snd)%3;
		if(w[v]<0) dfs(v, d2, s, f, es);
		else f &= (w[v]==d2);
	}
}

int main(){
	cin>>n>>m;
	rep(i, m){
		int a, b;
		cin>>a>>b;
		a--;
		b--;
		e[a].pb(P(b, 1));
		e[b].pb(P(a, 2));
	}
	mset(w, -1);
	ll res = 0;
	rep(i, n){
		ll s[3] = {};
		bool f = true;
		ll es = 0;
		if(w[i]<0){
			dfs(i, 0, s, f, es);
			if(f){
				if(s[0]&&s[1]&&s[2]) res += s[0]*s[1]+s[1]*s[2]+s[2]*s[0];
				else res += es/2;
			} else {
				ll t = s[0]+s[1]+s[2];
				res += t*t;
			}
		}
	}
	cout<<res<<endl;
	return 0;
}

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