Submission #536323

#	Time	Username	Problem	Language	Result	Execution time	Memory
536323		rainboy	우호 조약 체결 (JOI14_friends)	C11	100 / 100	77 ms	12764 KiB

friends

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

#define N	100000

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;
}

int ds[N], sz[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)
		return;
	if (ds[i] > ds[j])
		ds[i] = j, sz[j] += sz[i];
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i, sz[i] += sz[j];
	}
}

char visited[N];

void dfs(int i) {
	int o;

	if (visited[i])
		return;
	visited[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		join(i, j);
		dfs(j);
	}
}

int main() {
	int n, m, i, j, j_, o;
	long long ans;

	scanf("%d%d", &n, &m);
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	while (m--) {
		scanf("%d%d", &i, &j), i--, j--;
		append(i, j);
	}
	memset(ds, -1, n * sizeof *ds);
	for (i = 0; i < n; i++)
		sz[i] = 1;
	for (i = 0; i < n; i++)
		if (eo[i] >= 2) {
			j_ = ej[i][0];
			for (o = eo[i]; o--; ) {
				j = ej[i][o];
				join(j, j_);
			}
			for (o = eo[i]; o--; ) {
				j = ej[i][o];
				dfs(j);
			}
		}
	ans = 0;
	for (i = 0; i < n; i++)
		if (ds[i] < 0)
			ans += sz[i] == 1 ? eo[i] : (long long) sz[i] * (sz[i] - 1);
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

friends.c: In function 'append':
friends.c:12:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   12 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
friends.c: In function 'main':
friends.c:57:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
friends.c:61:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 30 / 30
• Subtask 3: 65 / 65