Submission #172521

#	Time	Username	Problem	Language	Result	Execution time	Memory
172521		eggag32	Duathlon (APIO18_duathlon)	C++17	0 / 100	1065 ms	1048580 KiB

count_triplets

#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> pi;
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) debug(x) debug(y);
#define repn(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(i, a) for(int i = 0; i < (int)(a); i++)
#define all(v) v.begin(), v.end() 
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define sq(x) ((x) * (x))

template<class T> T gcd(T a, T b){ return ((b == 0) ? a : gcd(b, a % b)); }

vi g[100005];
ll tmp = 0, ans = 0;

void dfs(int cur, int prev, vi cnt, vi vis){
	if(prev != -1){
		cnt[1] += cnt[0];
		cnt[0]++;
	}
	vis[cur] = 1;
	int f = 0;
	for(int u : g[cur]) if(!vis[u]) dfs(u, cur, cnt, vis), f = 1;
	if(!f) tmp += cnt[1];
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	//freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
	int n, m;
	cin >> n >> m;
	rep(i, m){
		int a, b;
		cin >> a >> b;
		a--, b--;
		g[a].pb(b);
		g[b].pb(a);
	}
	vi v(n, 0);
	rep(i, n){
		//we fix s to be i
		vi cnt(2, 0);
		tmp = 0;
		dfs(i, -1, cnt, v);
		ans += tmp;
	}
	cout << ans << endl;
	return 0;
}
/*
Things to look out for:
	- Integer overflows
	- Array bounds
	- Special cases
Be careful!
*/

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