Submission #430882

#	Time	Username	Problem	Language	Result	Execution time	Memory
430882		Kevin_Zhang_TW	Making Friends on Joitter is Fun (JOI20_joitter2)	C++17	0 / 100	9 ms	11212 KiB

joitter2

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
// My bug list :
// integer overflow
// 0based, 1based forgotten
// index out of bound
// n, m, i, j typo
// some cases are missing

const int MAX_N = 100010;

ll ans;

int n, m, g[MAX_N], sz[MAX_N];

unordered_set<int> out[MAX_N], in[MAX_N];

void init() {
	iota(g, g+n+1, 0);
	fill(sz, sz + n + 1, 1);
}

int F(int i) { return i == g[i] ? i : g[i] = F(g[i]); }

void clean(int a, int b) {
	vector<int> ina(AI(in[a]));
	for (int x : ina) {
		if (F(x) == F(b)) {
			in[a].erase(x);
			ans -= sz[ F(a) ];
			out[x].erase( F(a) );
		}
	}
}
void add_edge(int a, int b) {
	if (F(a) == F(b)) return;
	if (out[a].count(F(b))) return;

	bool mg = false;
	for (int x : in[ F(a) ]) if (F(x) == F(b)) {
		mg = true;
	}
	if (mg) {
		a = F(a), b = F(b);
		clean(a, b), clean(b, a);

		ans += 1ll * in[a].size() * sz[b] + 1ll * in[b].size() * sz[a] + 2ll * sz[a] * sz[b];

		for (int x : in[a]) {
			out[x].erase(a), out[x].insert(b);
			in[b].insert(x);
		}

		sz[b] += sz[a];
		g[a] = b;

		for (int x : in[b])
			add_edge(x, a), add_edge(x, b);
		return;
	}
	out[a].insert(F(b));
	ans += sz[ F(b) ];
	in[F(b)].insert(a);
}
int32_t main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> n >> m;
	init();
	while (m--) {
		int a, b;
		cin >> a >> b;
		//DE("edge ", a, b);
		add_edge(a, b);
		//for (int i = 1;i <= n;++i) DE(i, F(i));

		cout << ans << '\n';
		//DE(ans);
   	}

	for (int i = 1;i <= n;++i) for (int u : in[F(i)]) assert(F(i) != F(u));
}

• Subtask 1: 0 / 1
• Subtask 2: 0 / 16
• Subtask 3: 0 / 83