Submission #471230

#	Time	Username	Problem	Language	Result	Execution time	Memory
471230		rainboy	Usmjeri (COCI17_usmjeri)	C11	140 / 140	345 ms	57872 KiB

usmjeri

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

#define N	300000
#define MD	1000000007

int min(int a, int b) { return a < b ? a : b; }

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 dd[N], pp[N], qq[N], ta[N], inv[N], cnt;

int dfs1(int p, int i, int d) {
	int o, s, k_, j_;

	dd[i] = d, pp[i] = p;
	s = 1, k_ = 0, j_ = -1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			int k = dfs1(i, j, d + 1);

			s += k;
			if (k_ < k)
				k_ = k, j_ = j;
		}
	}
	qq[i] = j_;
	return s;
}

void dfs2(int p, int i, int q) {
	int j_, o;

	inv[ta[i] = cnt++] = i;
	j_ = qq[i], qq[i] = q;
	if (j_ != -1)
		dfs2(i, j_, q);
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p && j != j_)
			dfs2(i, j, j);
	}
}

int lca(int i, int j) {
	while (qq[i] != qq[j])
		if (dd[qq[i]] > dd[qq[j]])
			i = pp[qq[i]];
		else
			j = pp[qq[j]];
	return dd[i] < dd[j] ? i : j;
}

int ancestor(int i, int d) {
	while (dd[qq[i]] > d)
		i = pp[qq[i]];
	return inv[ta[i] - (dd[i] - d)];
}

int ds[N * 2];

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;
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i;
	}
}

int kk[N];

void dfs3(int p, int i) {
	int o;

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

		if (j != p) {
			dfs3(i, j);
			kk[i] += kk[j];
		}
	}
	if (kk[i] > 0)
		join(pp[i] << 1 | 0, i << 1 | 0), join(pp[i] << 1 | 1, i << 1 | 1);
}

int main() {
	int n, m, h, i, j, k, ans;

	scanf("%d%d", &n, &m);
	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);
	}
	dfs1(-1, 0, 0);
	dfs2(-1, 0, 0);
	memset(ds, -1, n * 2 * sizeof *ds);
	for (h = 0; h < m; h++) {
		int a, b, c;

		scanf("%d%d", &i, &j), i--, j--;
		a = lca(i, j), b = i == a ? a : ancestor(i, dd[a] + 1), c = j == a ? a : ancestor(j, dd[a] + 1);
		if (i != a && j != a)
			join(b << 1 | 0, c << 1 | 1), join(b << 1 | 1, c << 1 | 0);
		kk[i]++, kk[b]--, kk[j]++, kk[c]--;
	}
	dfs3(-1, 0);
	for (i = 0; i < n; i++)
		if (find(i << 1 | 0) == find(i << 1 | 1)) {
			printf("0\n");
			return 0;
		}
	k = 0;
	for (i = 0; i < n * 2; i++)
		if (ds[i] < 0)
			k++;
	k = k / 2 - 1;
	ans = 1;
	while (k--)
		ans = ans * 2 % MD;
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

usmjeri.c: In function 'append':
usmjeri.c:15:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   15 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
usmjeri.c: In function 'main':
usmjeri.c:112:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  112 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
usmjeri.c:116:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  116 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~
usmjeri.c:125:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  125 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 14
• Subtask 2: 14 / 14
• Subtask 3: 14 / 14
• Subtask 4: 14 / 14
• Subtask 5: 14 / 14
• Subtask 6: 14 / 14
• Subtask 7: 14 / 14
• Subtask 8: 14 / 14
• Subtask 9: 14 / 14
• Subtask 10: 14 / 14