Submission #957591

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Source Code Expand

#include "bits/stdc++.h"
using namespace std;
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
static const int INF = 0x3f3f3f3f; static const long long INFL = 0x3f3f3f3f3f3f3f3fLL;
typedef vector<int> vi; typedef pair<int, int> pii; typedef vector<pair<int, int> > vpii; typedef long long ll;
template<typename T, typename U> static void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> static void amax(T &x, U y) { if(x < y) x = y; }

struct UnionFind {
	vector<int> data;
	void init(int n) { data.assign(n, -1); }
	bool unionSet(int x, int y) {
		x = root(x); y = root(y);
		if(x != y) {
			if(data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) { return root(x) == root(y); }
	int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
	int size(int x) { return -data[root(x)]; }
};

int main() {
	int N; int E;
	while(~scanf("%d%d", &N, &E)) {
		UnionFind uf, uf3;
		uf.init(N);
		uf3.init(N * 3);
		vector<int> outdeg(N, 0), indeg(N, 0);
		vpii edges(E);
		rep(i, E) {
			int a; int b;
			scanf("%d%d", &a, &b), -- a, -- b;
			++ outdeg[a], ++ indeg[b];
			edges[i] = { a, b };
			uf.unionSet(a, b);
			rep(k, 3)
				uf3.unionSet(a * 3 + k, b * 3 + (k + 1) % 3);
		}
		sort(edges.begin(), edges.end());
		edges.erase(unique(edges.begin(), edges.end()), edges.end());

		vector<int> ccEdges(N, 0);
		for(auto e : edges)
			++ ccEdges[uf.root(e.first)];
		vector<bool> hasP3(N);
		rep(i, N) {
			if(indeg[i] > 0 && outdeg[i] > 0)
				hasP3[uf.root(i)] = true;
		}
		ll ans = 0;
		rep(i, N) if(uf.root(i) == i) {
			if(!hasP3[i])
				ans += ccEdges[i];
		}
		vector<int> cc3Size(N * 3);
		rep(i, N) if(hasP3[uf.root(i)]) {
			rep(k, 3) if(uf3.findSet(i * 3, uf.root(i) * 3 + k))
				++ cc3Size[uf.root(i) * 3 + k];
		}
		rep(i, N) if(uf.root(i) == i && hasP3[i]) {
			if(uf3.findSet(i * 3 + 0, i * 3 + 1)) {
				int n = cc3Size[i * 3 + 0];
				ans += (ll)n * n;
			} else {
				rep(k, 3)
					ans += (ll)cc3Size[i * 3 + k] * cc3Size[i * 3 + (k + 1) % 3];
			}
		}
		printf("%lld\n", ans);
	}
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:37:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d", &a, &b), -- a, -- b;
                                     ^

Judge Result