Submission #381179

#	Time	Username	Problem	Language	Result	Execution time	Memory
381179		rainboy	Duathlon (APIO18_duathlon)	C11	31 / 100	135 ms	63312 KiB

count_triplets

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

#define N	100000
#define M	200000

int ds[N], mm[N], nn[N];

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) {
		mm[i]++;
		return;
	}
	if (ds[i] > ds[j])
		ds[i] = j, mm[j] += mm[i] + 1, nn[j] += nn[i];
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i, mm[i] += mm[j] + 1, nn[i] += nn[j];
	}
}

int *ej[N], eo[N];

void append(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;
}

char visited[N]; int sz[N], qu[N], cnt;

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

	qu[cnt++] = i;
	visited[i] = 1;
	sz[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

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

int main() {
	static int dd[N];
	int n, m, h, i, j, pathcyc;
	long long ans;

	scanf("%d%d", &n, &m);
	memset(ds, -1, n * sizeof *ds);
	for (i = 0; i < n; i++) {
		nn[i] = 1;
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	}
	for (h = 0; h < m; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		dd[i]++, dd[j]++;
		join(i, j);
		append(i, j), append(j, i);
	}
	pathcyc = 1;
	for (i = 0; i < n; i++)
		if (dd[i] > 2) {
			pathcyc = 0;
			break;
		}
	if (pathcyc) {
		ans = 0;
		for (i = 0; i < n; i++)
			if (ds[i] < 0)
				ans += nn[i] == mm[i] ?  (long long) nn[i] * (nn[i] - 1) * (nn[i] - 2) : (long long) nn[i] * (nn[i] - 1) * (nn[i] - 2) / 3;
	} else {
		ans = 0;
		for (i = 0; i < n; i++)
			if (!visited[i]) {
				dfs(-1, i);
				ans += (long long) sz[i] * (sz[i] - 1) * (sz[i] - 2);
				while (--cnt) {
					j = qu[cnt];
					ans -= (long long) sz[j] * (sz[j] - 1) + (long long) (sz[i] - sz[j]) * (sz[i] - sz[j] - 1);
				}
			}
	}
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

count_triplets.c: In function 'append':
count_triplets.c:35:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   35 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
count_triplets.c: In function 'main':
count_triplets.c:63:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   63 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
count_triplets.c:70:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   70 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 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