Submission #545884

#	Time	Username	Problem	Language	Result	Execution time	Memory
545884		rainboy	007 (CEOI14_007)	C11	100 / 100	306 ms	23228 KiB

007

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

#define N	200000

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;
}

void bfs(int *dd, int n, int s) {
	static int qu[N];
	int i, head, cnt;

	for (i = 0; i < n; i++)
		dd[i] = n;
	head = cnt = 0;
	dd[s] = 0, qu[head + cnt++] = s;
	while (cnt) {
		int d, o;

		i = qu[cnt--, head++], d = dd[i] + 1;
		for (o = eo[i]; o--; ) {
			int j = ej[i][o];

			if (dd[j] > d)
				dd[j] = d, qu[head + cnt++] = j;
		}
	}
}

int dda[N], ddb[N], dd_[N]; char visited[N];

void dfs(int i) {
	int o;

	if (visited[i])
		return;
	dd_[i] = dda[i], visited[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (dda[j] == dda[i] - 1 && ddb[j] == ddb[i] - 1) {
			dfs(j);
			dd_[i] = min(dd_[i], dd_[j]);
		}
	}
}

int main() {
	int n, m, s, t, a, b, i, j, d;

	scanf("%d%d%d%d%d%d", &n, &m, &s, &t, &a, &b), s--, t--, a--, b--;
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	while (m--) {
		scanf("%d%d", &i, &j), i--, j--;
		append(i, j), append(j, i);
	}
	bfs(dda, n, a);
	bfs(ddb, n, b);
	d = dda[s] > dda[t] || ddb[s] > ddb[t] ? -1 : min(dda[t] - dda[s], ddb[t] - ddb[s]);
	if (d != -1 && dda[s] == ddb[s] && dda[t] == ddb[t]) {
		dfs(s), dfs(t);
		if (dd_[s] > dd_[t])
			d--;
	}
	printf("%d\n", d);
	return 0;
}

Compilation message (stderr)

007.c: In function 'append':
007.c:13:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   13 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
007.c: In function 'main':
007.c:60:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |  scanf("%d%d%d%d%d%d", &n, &m, &s, &t, &a, &b), s--, t--, a--, b--;
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
007.c:64:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70