Submission #241705

#	Time	Username	Problem	Language	Result	Execution time	Memory
241705		atoiz	Duathlon (APIO18_duathlon)	C++14	0 / 100	72 ms	17412 KiB

count_triplets

/*input
4 4
1 2
2 3
3 4
4 2

4 3
1 2
3 4
4 1

5 4
1 2
2 3
3 4
4 5

4 3
1 2
2 3
3 4

*/

#include <stdio.h>

#define N 100007
#define M 400007
int n, m, to[M], nx[M], st[N], low[N], vis[N], ts, stk[N], instack[N], *top = &stk[0];
int bto[N * 4], bnx[N * 4], bst[N * 2], b, bm, bsz[N * 2];
long long ans = 0;

inline void minimize(int &i, int j) { (i > j ? i = j : 0); }

void build(int u, int p)
{
	low[u] = vis[u] = ++ts;
	instack[*(++top) = u] = 1;

	int i, v, w, c = 0;
	for (i = st[u]; i; i = nx[i]) if (to[i] != p) {
		v = to[i];
		if (!vis[v]) {
			++c;
			build(v, u);
			if (low[v] >= vis[u]) {
				++b;
				bool cont = true;
				while (cont) {
					instack[w = (*top--)] = 0;
					cont = (w != v);
					++bm, bnx[bm] = bst[w], bto[bst[w] = bm] = b;
					++bm, bnx[bm] = bst[b], bto[bst[b] = bm] = w;
				}
				++bm, bnx[bm] = bst[b], bto[bst[b] = bm] = u;
				++bm, bnx[bm] = bst[u], bto[bst[u] = bm] = b;
			}
			minimize(low[u], low[v]);
		} else if (instack[v]) {
			minimize(low[u], vis[v]);
		}
	}
}

void solve(int u, int p)
{
	int i, v, d = 0;
	long long x = 0;

	bsz[u] = (u <= n);
	for (i = bst[u]; i; i = bnx[i]) if (bto[i] != p) {
		solve(v = bto[i], u), bsz[u] += bsz[v], ++d;
		x += (long long) bsz[v] * (bsz[v] - 1);
	}

	if (u > n) {
		x += (long long) (n - bsz[u]) * (n - bsz[u] - 1);
		ans -= x * d;
	}
}

int main()
{
	int i, u, v;
	scanf("%d %d", &n, &m);
	for (i = 1; i <= m; ++i) {
		scanf("%d %d", &u, &v);
		nx[i * 2] = st[u], to[st[u] = i * 2] = v;
		nx[i * 2 - 1] = st[v], to[st[v] = i * 2 - 1] = u;
	}

	b = n, build(1, 0);
	ans = (long long) n * (n - 1) * (n - 2), solve(1, 0);
	printf("%lld", ans);
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:86:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
count_triplets.cpp:88:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~~

• 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