Submission #832773

#	Time	Username	Problem	Language	Result	Execution time	Memory
832773		rainboy	Relay Marathon (NOI20_relaymarathon)	C11	100 / 100	1858 ms	120776 KiB

RelayMarathon

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

#define N	100000
#define M	3000000
#define INF	0x3f3f3f3f

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

char special[N]; int n;
int ii[M], jj[M], ww[M], m;

int *eh[N], eo[N];

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

	if (o >= 2 && (o & o - 1) == 0)
		eh[i] = (int *) realloc(eh[i], o * 2 * sizeof *eh[i]);
	eh[i][o] = h;
}

int dd[N], rr[N], iq[N + 1], pq[N], cnt;

int lt(int i, int j) { return dd[i] < dd[j]; }

int p2(int p) {
	return (p *= 2) > cnt ? 0 : (p < cnt && lt(iq[p + 1], iq[p]) ? p + 1 : p);
}

void pq_up(int i) {
	int p, q, j;

	for (p = pq[i]; (q = p / 2) && lt(i, j = iq[q]); p = q)
		iq[pq[j] = p] = j;
	iq[pq[i] = p] = i;
}

void pq_dn(int i) {
	int p, q, j;

	for (p = pq[i]; (q = p2(p)) && lt(j = iq[q], i); p = q)
		iq[pq[j] = p] = j;
	iq[pq[i] = p] = i;
}

void pq_add(int i) {
	pq[i] = ++cnt, pq_up(i);
}

int pq_remove_first() {
	int i = iq[1], j = iq[cnt--];

	if (j != i)
		pq[j] = 1, pq_dn(j);
	pq[i] = 0;
	return i;
}

void dijkstra() {
	int i, o;

	memset(pq, 0, n * sizeof *pq), cnt = 0;
	for (i = 0; i < n; i++)
		pq_add(i);
	while (cnt) {
		i = pq_remove_first();
		for (o = eo[i]; o--; ) {
			int h = eh[i][o], j = i ^ ii[h] ^ jj[h], d = dd[i] + ww[h];

			if (dd[j] > d)
				dd[j] = d, rr[j] = rr[i], pq_up(j);
		}
	}
}

int main() {
	int k, h, i, i_, i1, j, j_, j1, w, d, d1, d2, di1, di2, dj1, dj2, ans;

	scanf("%d%d%d", &n, &m, &k);
	for (i = 0; i < n; i++)
		eh[i] = (int *) malloc(2 * sizeof *eh[i]);
	for (h = 0; h < m; h++) {
		scanf("%d%d%d", &i, &j, &w), i--, j--;
		ii[h] = i, jj[h] = j, ww[h] = w;
		append(i, h), append(j, h);
	}
	while (k--) {
		scanf("%d", &i), i--;
		special[i] = 1;
	}
	for (i = 0; i < n; i++)
		dd[i] = special[i] ? 0 : INF, rr[i] = i;
	dijkstra();
	d1 = INF, i_ = j_ = -1;
	for (h = 0; h < m; h++) {
		i = ii[h], j = jj[h];
		if (rr[i] != rr[j] && d1 > (d = dd[i] + ww[h] + dd[j]))
			d1 = d, i_ = rr[i], j_ = rr[j];
	}
	for (i = 0; i < n; i++)
		dd[i] = special[i] && i != i_ && i != j_ ? 0 : INF, rr[i] = i;
	dijkstra();
	d2 = INF;
	for (h = 0; h < m; h++) {
		i = ii[h], j = jj[h];
		if (rr[i] != rr[j])
			d2 = min(d2, dd[i] + ww[h] + dd[j]);
	}
	ans = d1 + d2;
	for (i = 0; i < n; i++)
		dd[i] = i == i_ ? 0 : INF, rr[i] = i;
	dijkstra();
	di1 = di2 = INF, j1 = -1;
	for (j = 0; j < n; j++)
		if (special[j] && j != i_ && j != j_) {
			if (di1 > dd[j])
				di2 = di1, di1 = dd[j], j1 = j;
			else if (di2 > dd[j])
				di2 = dd[j];
		}
	for (i = 0; i < n; i++)
		dd[i] = i == j_ ? 0 : INF, rr[i] = i;
	dijkstra();
	dj1 = dj2 = INF, i1 = -1;
	for (i = 0; i < n; i++)
		if (special[i] && i != i_ && i != j_) {
			if (dj1 > dd[i])
				dj2 = dj1, dj1 = dd[i], i1 = i;
			else if (dj2 > dd[i])
				dj2 = dd[i];
		}
	if (i1 != j1)
		ans = min(ans, di1 + dj1);
	else
		ans = min(ans, min(di1 + dj2, di2 + dj1));
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

RelayMarathon.c: In function 'append':
RelayMarathon.c:19:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   19 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
RelayMarathon.c: In function 'main':
RelayMarathon.c:81:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |  scanf("%d%d%d", &n, &m, &k);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
RelayMarathon.c:85:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   85 |   scanf("%d%d%d", &i, &j, &w), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
RelayMarathon.c:90:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |   scanf("%d", &i), i--;
      |   ^~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 25 / 25
• Subtask 4: 58 / 58