Submission #922618

#	Time	Username	Problem	Language	Result	Execution time	Memory
922618		rainboy	Travels (LMIO17_keliones)	C11	100 / 100	64 ms	23888 KiB

keliones

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

#define N	200000
#define MD	1000000007

void append(int **ej, int *eo, 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 main() {
	static int ww[N], *ej[N], eo[N], *fi[N], fo[N], dp[N], dq[N];
	int n, m, h, i, j, o, sum, ans;

	scanf("%d%d", &n, &m);
	for (i = 0; i < n; i++)
		scanf("%d", &ww[i]);
	for (i = 0; i < n; i++) {
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
		fi[i] = (int *) malloc(2 * sizeof *fi[i]);
	}
	for (h = 0; h < m; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		append(ej, eo, i, j), append(fi, fo, j, i);
	}
	sum = 0;
	for (j = 0; j < n; j++) {
		dp[j] = (sum + 1) % MD;
		for (o = fo[j]; o--; ) {
			i = fi[j][o];
			dp[j] = (dp[j] - dp[i] + MD) % MD;
		}
		sum = (sum + dp[j]) % MD;
	}
	sum = 0;
	for (i = n - 1; i >= 0; i--) {
		dq[i] = (sum + 1) % MD;
		for (o = eo[i]; o--; ) {
			j = ej[i][o];
			dq[i] = (dq[i] - dq[j] + MD) % MD;
		}
		sum = (sum + dq[i]) % MD;
	}
	ans = 0;
	for (i = 0; i < n; i++)
		ans = (ans + ww[i] * (((long long) dp[i] * dq[i] - 1 + MD) % MD)) % MD;
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

keliones.c: In function 'append':
keliones.c:10:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   10 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
keliones.c: In function 'main':
keliones.c:19:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
keliones.c:21:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |   scanf("%d", &ww[i]);
      |   ^~~~~~~~~~~~~~~~~~~
keliones.c:27:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 25 / 25
• Subtask 4: 55 / 55