Submission #832792

#	Time	Username	Problem	Language	Result	Execution time	Memory
832792		rainboy	Firefighting (NOI20_firefighting)	C11	100 / 100	268 ms	48492 KiB

Firefighting

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

#define N	300000
#define INF	0x3f3f3f3f3f3f3f3fLL

long long min(long long a, long long b) { return a < b ? a : b; }
long long max(long long a, long long b) { return a > b ? a : b; }

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

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

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

long long dp[N], dq[N], d; int qu[N], cnt;

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

	dp[i] = -1, dq[i] = INF;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o], w = ew[i][o];

		if (j != p) {
			dfs(i, j);
			if (dp[j] != -1) {
				if (dp[j] + w > d)
					qu[cnt++] = j, dq[j] = 0;
				else
					dp[i] = max(dp[i], dp[j] + w);
			}
			dq[i] = min(dq[i], dq[j] + w);
		}
	}
	if (dp[i] != -1 && dp[i] + dq[i] <= d)
		dp[i] = -1;
	if (dq[i] > d)
		dp[i] = max(dp[i], 0);
}

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

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

Compilation message (stderr)

Firefighting.c: In function 'append':
Firefighting.c:15:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   15 |  if (o >= 2 && (o & o - 1) == 0) {
      |                     ~~^~~
Firefighting.c: In function 'main':
Firefighting.c:51:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |  scanf("%d%lld", &n, &d);
      |  ^~~~~~~~~~~~~~~~~~~~~~~
Firefighting.c:57:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |   scanf("%d%d%d", &i, &j, &w), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 3 / 3
• Subtask 2: 5 / 5
• Subtask 3: 9 / 9
• Subtask 4: 19 / 19
• Subtask 5: 26 / 26
• Subtask 6: 38 / 38