Submission #412225

#	Time	Username	Problem	Language	Result	Execution time	Memory
412225		rainboy	Traffic (IOI10_traffic)	C11	100 / 100	845 ms	144052 KiB

traffic

#include "traffic.h"
#include <stdlib.h>

#define N	1000000

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 sz[N], sum, c;

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

	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs(i, j);
			sz[i] += sz[j];
		}
	}
	if (sz[i] >= (sum + 1) / 2 && (c == -1 || sz[c] > sz[i]))
		c = i;
}

int LocateCentre(int n, int *aa, int *ii, int *jj) {
	int h, i;

	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (h = 0; h < n - 1; h++)
		append(ii[h], jj[h]), append(jj[h], ii[h]);
	sum = 0;
	for (i = 0; i < n; i++)
		sum += aa[i], sz[i] = aa[i];
	c = -1, dfs(-1, 0);
	return c;
}

Compilation message (stderr)

traffic.c: In function 'append':
traffic.c:11:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   11 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~

• Subtask 1: 25 / 25
• Subtask 2: 25 / 25
• Subtask 3: 25 / 25
• Subtask 4: 25 / 25