Submission #545888

#	Time	Username	Problem	Language	Result	Execution time	Memory
545888		rainboy	Pipes (CEOI15_pipes)	C11	40 / 100	1384 ms	65536 KiB

pipes

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define N	100000
#define M	((N - 1) * 2)
 
int min(int a, int b) { return a < b ? a : b; }
 
int ii[M], jj[M]; char bridge[M];
int *eh[N], eo[N];
 
void append(int i, int h) {
	eh[i][eo[i]++] = h;
}
 
int find(int *ds, int i) {
	return ds[i] < 0 ? i : (ds[i] = find(ds, ds[i]));
}

int join(int *ds, int i, int j) {
	i = find(ds, i), j = find(ds, j);
	if (i == j)
		return 0;
	if (ds[i] > ds[j])
		ds[i] = j;
	else {
		if (ds[i] == ds[j])
			ds[i]--;
		ds[j] = i;
	}
	return 1;
}
 
int ta[N], tb[N];
 
void dfs(int f, int i) {
	static int time;
	int o;
 
	ta[i] = tb[i] = ++time;
	for (o = eo[i]; o--; ) {
		int h = eh[i][o], j = i ^ ii[h] ^ jj[h];
 
		if (h != f) {
			if (!ta[j]) {
				dfs(h, j);
				tb[i] = min(tb[i], tb[j]);
				if (tb[j] == ta[j])
					bridge[h] = 1;
			} else
				tb[i] = min(tb[i], ta[j]);
		}
	}
}
 
int main() {
	static int ds1[N], ds2[N];
	int n, m, m_, h, i, j;
 
	scanf("%d%d", &n, &m);
	memset(ds1, -1, n * sizeof *ds1);
	memset(ds2, -1, n * sizeof *ds2);
	m_ = 0;
	while (m--) {
		scanf("%d%d", &i, &j), i--, j--;
		if (join(ds1, i, j) || join(ds2, i, j)) {
			ii[m_] = i, jj[m_] = j, m_++;
			eo[i]++, eo[j]++;
		}
	}
	m = m_;
	for (i = 0; i < n; i++)
		eh[i] = (int *) malloc(eo[i] * sizeof *eh[i]), eo[i] = 0;
	for (h = 0; h < m; h++)
		append(ii[h], h), append(jj[h], h);
	for (i = 0; i < n; i++)
		if (!ta[i])
			dfs(-1, i);
	for (h = 0; h < m; h++)
		if (bridge[h])
			printf("%d %d\n", ii[h] + 1, jj[h] + 1);
	return 0;
}

Compilation message (stderr)

pipes.c: In function 'main':
pipes.c:61:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
pipes.c:66:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10