제출 #296013

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
296013		srvlt	철인 이종 경기 (APIO18_duathlon)	C++14	10 / 100	24 ms	512 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define all(x) begin(x), end(x)
#define SZ(x) (int)(x).size()
#define cps(x) sort(all(x)), (x).erase(unique(all(x)), end(x))
#define cps2(x, y) sort(all(x), y), (x).erase(unique(all(x)), end(x))
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int n0 = 1003;
int n, m, root, used[n0], anc[n0], sz[n0], back, comp;
vector <int> g[n0];

void dfs(int v, int p) {
	used[v] = 1;
	comp++;
	if (v != root) {
		if (p == root)
			anc[v] = v;
		else
			anc[v] = anc[p];
		sz[anc[v]]++;
	}
	for (int to : g[v]) {
		if (to == p) continue;
		if (used[to] == 1 && to == root) {
			sz[anc[v]]--;
			back++;
		}
		if (!used[to])
			dfs(to, v);
	}
	used[v] = 2;
}

int main() {
	ios_base::sync_with_stdio(false), cin.tie(NULL);
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		int x, y;
		cin >> x >> y;
		g[x].pb(y), g[y].pb(x);
	}
	ll res = 0;
	for (int i = 1; i <= n; i++) {
		root = i;
		comp = 0;
		memset(& used, 0, sizeof(used));
		memset(& anc, 0, sizeof(anc));
		memset(& sz, 0, sizeof(sz));
		back = 0;
		dfs(i, -1);
		for (int j = 1; j <= n; j++)
			res += sz[j] * (comp - 1 - sz[j]);
		res += back * (comp - 2);
	}
	cout << res;
}

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