Submission #381212

#	Time	Username	Problem	Language	Result	Execution time	Memory
381212		rainboy	Duathlon (APIO18_duathlon)	C11	100 / 100	188 ms	32492 KiB

count_triplets

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define N	100000
#define M	200000

int min(int a, int b) { return a < b ? a : b; }

int ds[M];

int find(int i) {
	return ds[i] < 0 ? i : (ds[i] = find(ds[i]));
}

void join(int i, int j) {
	i = find(i);
	j = find(j);
	if (i == j)
		return;
	if (ds[i] > ds[j])
		ds[i] = j;
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i;
	}
}

int ij[M];
int *eh[N], eo[N], *ej[M + N], eo_[M + N];

void append(int **ej, int *eo, int i, int j) {
	int o = eo[i]++;

	if (o >= 2 && (o & o - 1) == 0)
		ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
	ej[i][o] = j;
}

int ta[N], tb[N];

void dfs1(int f, int i) {
	static int time;
	int o;

	ta[i] = tb[i] = ++time;
	for (o = eo[i]; o--; ) {
		int h = eh[i][o], j = i ^ ij[h];

		if (h != f) {
			if (!ta[j]) {
				dfs1(h, j);
				if (tb[j] < ta[i])
					join(h, f);
				tb[i] = min(tb[i], tb[j]);
			} else if (ta[j] < ta[i]) {
				tb[i] = min(tb[i], ta[j]);
				join(h, f);
			}
		}
	}
}

char visited[M + N]; int pp[M + N], sz[M + N], qu[M + N], cnt;
long long ans;

void dfs2(int p, int i) {
	int o;

	qu[cnt++] = i;
	visited[i] = 1, pp[i] = p;
	for (o = eo_[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs2(i, j);
			sz[i] += sz[j];
		}
	}
}

int main() {
	static char used[M];
	int n, m, h, i, i_, j;

	scanf("%d%d", &n, &m);
	for (i = 0; i < n; i++)
		eh[i] = (int *) malloc(2 * sizeof *eh[i]);
	for (h = 0; h < m; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		ij[h] = i ^ j;
		append(eh, eo, i, h), append(eh, eo, j, h);
	}
	memset(ds, -1, m * sizeof *ds);
	for (i = 0; i < n; i++)
		if (!ta[i])
			dfs1(-1, i);
	for (i = 0; i < m + n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (i = 0; i < n; i++) {
		int o, h_;

		h_ = -1;
		for (o = eo[i]; o--; ) {
			h = find(eh[i][o]);
			if (!used[h]) {
				used[h] = 1;
				append(ej, eo_, m + i, h), append(ej, eo_, h, m + i);
				if (h_ == -1)
					h_ = h;
				else
					h_ = -2;
			}
		}
		for (o = eo[i]; o--; ) {
			h = find(eh[i][o]);
			used[h] = 0;
		}
		sz[m + i] = 1;
	}
	for (i_ = 0; i_ < m + n; i_++)
		if (!visited[i_]) {
			int n_;

			cnt = 0, dfs2(-1, i_);
			n_ = sz[i_];
			ans += (long long) n_ * (n_ - 1) * (n_ - 2);
			while (cnt--) {
				int o;

				i = qu[cnt];
				if (i < m)
					for (o = eo_[i]; o--; ) {
						int s;

						j = ej[i][o], s = j == pp[i] ? n_ - sz[i] : sz[j];
						ans -= (long long) (eo_[i] - 1) * s * (s - 1);
					}
			}
		}
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

count_triplets.c: In function 'append':
count_triplets.c:36:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   36 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
count_triplets.c: In function 'main':
count_triplets.c:87:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   87 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
count_triplets.c:91:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   91 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

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