Submission #831438

#	Time	Username	Problem	Language	Result	Execution time	Memory
831438		rainboy	LOSTIKS (INOI20_lostiks)	C11	100 / 100	1604 ms	246508 KiB

Main

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

#define N	1000000
#define M	20
#define INF	0x3f3f3f3f

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

int n, m;

int *ej[N], *eg[N], eo[N];
int uu[M], vv[M];

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

	if (o >= 2 && (o & o - 1) == 0) {
		ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
		eg[i] = (int *) realloc(eg[i], o * 2 * sizeof *eg[i]);
	}
	ej[i][o] = j, eg[i][o] = g;
}

int dd[N], pp[N], qq[N], bb[N];

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

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

		if (j != p) {
			int k = dfs1(i, j, d + 1, g == -1 ? b : b | 1 << g);

			s += k;
			if (k_ < k)
				k_ = k, j_ = j;
			if (g != -1)
				vv[g] = i;
		}
	}
	qq[i] = j_;
	return s;
}

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

	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 dist(int i, int j) {
	return dd[i] + dd[j] - dd[lca(i, j)] * 2;
}

int main() {
	static int dds[M], ddt[M], ddd[M][M], bb_[M], dp[1 << M][M], gg[M];
	int k, g, g_, h, i, j, u, b, s, t, d, ans;

	scanf("%d%d%d", &n, &s, &t), s--, t--;
	for (i = 0; i < n; i++) {
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
		eg[i] = (int *) malloc(2 * sizeof *eg[i]);
	}
	m = 0;
	for (h = 0; h < n - 1; h++) {
		scanf("%d%d%d", &i, &j, &u), i--, j--, u--;
		if (u == -1)
			g = -1;
		else
			uu[g = m++] = u;
		append(i, j, g), append(j, i, g);
	}
	dfs1(-1, s, 0, 0);
	dfs2(-1, s, s);
	if (bb[t] == 0) {
		printf("%d\n", dd[t]);
		return 0;
	}
	for (g_ = 0; g_ < m; g_++) {
		d = dist(uu[g_], vv[g_]);
		dds[g_] = dd[uu[g_]] + d;
		for (g = 0; g < m; g++)
			ddd[g][g_] = dist(vv[g], uu[g_]) + d;
	}
	for (g = 0; g < m; g++)
		ddt[g] = dist(vv[g], t);
	for (g = 0; g < m; g++)
		bb_[g] = bb[uu[g]] | bb[vv[g]];
	for (b = 1; b < 1 << m; b++)
		memset(dp[b], 0x3f, m * sizeof *dp[b]);
	for (g = 0; g < m; g++)
		if (bb_[g] == 0)
			dp[1 << g][g] = dds[g];
	ans = INF;
	for (b = 1; b < 1 << m; b++) {
		k = 0;
		for (g = 0; g < m; g++)
			if ((b & 1 << g) == 0 && (bb_[g] & b) == bb_[g])
				gg[k++] = g;
		for (g = 0; g < m; g++) {
			int x = dp[b][g];

			if (x == INF)
				continue;
			if ((bb[t] & b) == bb[t])
				ans = min(ans, x + ddt[g]);
			for (h = 0; h < k; h++) {
				g_ = gg[h];
				dp[b | 1 << g_][g_] = min(dp[b | 1 << g_][g_], x + ddd[g][g_]);
			}
		}
	}
	if (ans == INF)
		ans = -1;
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

Main.c: In function 'append':
Main.c:19:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   19 |  if (o >= 2 && (o & o - 1) == 0) {
      |                     ~~^~~
Main.c: In function 'main':
Main.c:81:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |  scanf("%d%d%d", &n, &s, &t), s--, t--;
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
Main.c:88:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |   scanf("%d%d%d", &i, &j, &u), i--, j--, u--;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 23 / 23
• Subtask 2: 36 / 36
• Subtask 3: 41 / 41