Submission #544720

#	Time	Username	Problem	Language	Result	Execution time	Memory
544720		rainboy	Network (BOI15_net)	C11	100 / 100	359 ms	45840 KiB

net

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

#define N	500000

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 qu[N], cnt;

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

	if (eo[i] == 1)
		qu[cnt++] = i;
	for (o = 0; o < eo[i]; o++) {
		int j = ej[i][o];

		if (j != p)
			dfs(i, j);
	}
}

int main() {
	int n, h, i, j;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (h = 0; h < n - 1; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		append(i, j), append(j, i);
	}
	i = 0;
	while (eo[i] == 1)
		i++;
	dfs(-1, i);
	printf("%d\n", (cnt + 1) / 2);
	for (h = 0; h < (cnt + 1) / 2; h++)
		printf("%d %d\n", qu[h] + 1, qu[h + cnt / 2] + 1);
	return 0;
}

Compilation message (stderr)

net.c: In function 'append':
net.c:11:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   11 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
net.c: In function 'main':
net.c:34:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
net.c:38:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37