Submission #1201703

#	Time	Username	Problem	Language	Result	Execution time	Memory
1201703		crispxx	Duathlon (APIO18_duathlon)	C++20	10 / 100	1094 ms	11232 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define all(x) x.begin(), x.end()
#define pb push_back
#define ar array
#define nl '\n'

template <typename A, typename B>
bool chmin(A &a, const B &b) {
	if(a > b) {
		return a = b, true;
	}
	return false;
}

template <typename A, typename B>
bool chmax(A &a, const B &b) {
	if(a < b) {
		return a = b, true;
	}
	return false;
}

struct DSU {
	int n; vector<int> p, sz;
	DSU(int n) : n(n), p(n), sz(n, 1) {
		iota(all(p), 0);
	}
	int find(int v) {
		return v == p[v] ? v : p[v] = find(p[v]);
	}
	void unite(int u, int v) {
		u = find(u), v = find(v);
		if(u == v) return;
		if(sz[u] < sz[v]) swap(u, v);
		sz[u] += sz[v];
		p[v] = u;
	}
};

void solve() {
	int n, m; cin >> n >> m;
	
	vector<vector<int>> adj(n);
	
	vector<pair<int, int>> edges;
	
	for(int i = 0; i < m; i++) {
		int u, v; cin >> u >> v;
		edges.pb({u, v});
		adj[--u].pb(--v);
		adj[v].pb(u);
	}
	
	auto solve1 = [&]() {
		int ans = 0;
		
		for(int u = 0; u < n; u++) {
			queue<int> q;
			vector<int> d(n, -1), sum(n);
			q.emplace(u);
			d[u] = 0;
			while(!q.empty()) {
				int v = q.front();
				q.pop();
				ans += sum[v];
				for(auto to : adj[v]) {
					if(d[to] == -1) {
						d[to] = d[v] + 1;
						sum[to] += d[v];
						q.emplace(to);
					}
				}
			}
		}
		
		return ans;
	};
	
	auto solve2 = [&]() {
		int ans = 0;
		
		for(int i = 0; i < n; i++) {
			for(int j = 0; j < n; j++) {
				DSU d1(n), d2(n);
				for(auto [u, v] : edges) {
					if(u != i && v != i) d1.unite(u, v);
					if(u != j && v != j) d2.unite(u, v);
				}
				for(int v = 0; v < n; v++) {
					if(d1.find(j) == d1.find(v) && d2.find(i) == d2.find(v)) {
						ans++;
					}
				}
			}
		}
		
		return ans;
	};
	
	auto print = [&](int x) {
		cout << x << nl;
	};
	
	if(n <= 1000) {
		print(solve1());
		return;
	}
	
	print(solve2());
}

/**
4 3
1 2
2 3
3 4

4 4
1 2
2 3
3 4
4 2

**/

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	solve();
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 10 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10