Submission #648027

#	Time	Username	Problem	Language	Result	Execution time	Memory
648027		baojiaopisu	Duathlon (APIO18_duathlon)	C++14	23 / 100	117 ms	27692 KiB

count_triplets

#include<bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;

#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz

#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (x > y)
        {
            x = y;
            return true;
        }
        return false;
    }
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (x < y)
        {
            x = y;
            return true;
        }
        return false;
    }

const int MOD = 1e9 + 7; //998244353

template<class X, class Y>
	void add(X &x, const Y &y) {
		x = (x + y);
		if(x >= MOD) x -= MOD;
	}

template<class X, class Y> 
	void sub(X &x, const Y &y) {
		x = (x - y);
		if(x < 0) x += MOD;
	}

/* Author : Le Ngoc Bao Anh, 12A5, LQD High School for Gifted Student*/

const ll INF = 1e9;
const int N = 1e5 + 10;

vector<int> tree[N], g[N], adj[N];
int Time = 0;
int Low[N], Num[N], in[N], out[N], sz[N], up_node[N], depth[N];
vector<int> node;

void dfs(int u, int par) {
	Low[u] = Num[u] = ++Time;
	in[u] = Time;
	sz[u] = 1;
	node.pb(u);
	for(auto v : g[u]) {
		if(v != par) {
			if(Num[v]) {
				if(minimize(Low[u], Num[v])) up_node[u] = v;
				if(Num[v] < Num[u]) adj[v].pb(u);
			} else {
				tree[u].pb(v);
				tree[v].pb(u);
				depth[v] = depth[u] + 1;
				dfs(v, u);
				sz[u] += sz[v];
				if(minimize(Low[u], Low[v])) up_node[u] = up_node[v];
			}
		}
	}
	out[u] = Time;
}

template <class T> struct FenwickTree {
	int n;
	vector<T> bit;

	FenwickTree(int _n = 0) {
		n = _n;
		bit.resize(n + 5);
		for(int i = 1; i <= n; i++) bit[i] = 0;
	}

	void update(int pos, T x) {
		for(int i = pos; i <= n; i += i & (-i)) bit[i] += x;
	}

	T get(int pos) {
		T ans = 0;
		for(int i = pos; i > 0; i -= i & (-i)) ans += bit[i];
		return ans;
	}
};

void solve() {
	int n, m; cin >> n >> m;
	for(int i = 1; i <= m; i++) {
		int u, v; cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
	}

	FenwickTree<int> BIT = FenwickTree<int>(n);
	ll ans = 0;
	for(int i = 1; i <= n; i++) {
		if(!Num[i]) {
			depth[1] = 1;
			node.clear();
			dfs(i, 0);
			int c = node.size();
			for(auto u : node) {
				ans += 1ll * (c - sz[u]) * (sz[u] - 1);
				if(up_node[u]) {
					ans += 1ll * (c - sz[u]) * (c - sz[u] - 1) / 2;
					int v = up_node[u];
					ans -= 1ll * (c - sz[v] + 1) * (c - sz[v]) / 2;
				}
				ans += 1ll * (sz[u] - 1) * (sz[u] - 2) / 2;

				sort(all(adj[u]), [&](int x, int y) {
					return depth[x] > depth[y];
				});
				
				for(auto v : adj[u]) {
					if(BIT.get(out[v]) - BIT.get(in[v] - 1) == 0) {
						ans -= 1ll * sz[v] * (sz[v] - 1) / 2;
					}
					BIT.update(in[v], 1);
				}

				for(auto v : tree[u]) {
					if(depth[v] > depth[u] && (BIT.get(out[v]) - BIT.get(in[v] - 1)) == 0) {
						ans -= 1ll * sz[v] * (sz[v] - 1) / 2;
					}
				}

				for(auto v : adj[u]) BIT.update(in[v], -1);
			}
		}
	}

	cout << ans * 2 << '\n';
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:173:17: warning: unused variable 'ddd' [-Wunused-variable]
  173 |     int tc = 1, ddd = 0;
      |                 ^~~

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