Submission #722703

#	Time	Username	Problem	Language	Result	Execution time	Memory
722703		rainboy	Winter Driving (CCO19_day1problem3)	C11	25 / 25	130 ms	30828 KiB

Main

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

#define N	200000
#define M	36
#define K	(1 << M / 2)

long long max(long long a, long long 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 aa[N], c; long long dp[N], dq[N], sum, sum_;

void dfs1(int p, int i) {
	int o, centroid;

	dp[i] = aa[i], centroid = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs1(i, j);
			dp[i] += dp[j];
			if (dp[j] * 2 > sum)
				centroid = 0;
		}
	}
	if ((sum - dp[i]) * 2 > sum)
		centroid = 0;
	if (centroid)
		c = i;
}

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

	dp[i] = aa[i], dq[i] = 0;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs2(i, j);
			dp[i] += dp[j], dq[i] += dq[j];
		}
	}
	dq[i] += aa[i] * dp[i];
}

void brute(long long *ww, long long *ss, int m) {
	static long long ss_[K];
	int g1, g2, g, h;

	ss[0] = 0;
	for (h = 0; h < m; h++) {
		g1 = 0, g2 = 0, g = 0;
		while (g < (1 << h + 1))
			ss_[g++] = g2 == (1 << h) || g1 < (1 << h) && ss[g1] < ss[g2] + ww[h] ? ss[g1++] : ss[g2++] + ww[h];
		memcpy(ss, ss_, (1 << h + 1) * sizeof *ss_);
	}
}

int main() {
	static long long ww[M], ss1[K], ss2[K];
	int n, m, m1, m2, g1, g2, h, i, j;
	long long ans;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (i = 0; i < n; i++)
		scanf("%d", &aa[i]);
	for (j = 1; j < n; j++) {
		scanf("%d", &i), i--;
		append(i, j), append(j, i);
	}
	for (i = 0; i < n; i++)
		sum += aa[i];
	dfs1(-1, 0);
	dfs2(-1, c);
	m = eo[c], m1 = m / 2, m2 = m - m1;
	for (h = 0; h < m; h++) {
		j = ej[c][h];
		sum_ += ww[h] = dp[j];
	}
	brute(ww, ss1, m1);
	brute(ww + m1, ss2, m2);
	g1 = 0, g2 = (1 << m2) - 1, ans = 0;
	while (g1 < 1 << m1 && g2 >= 0) {
		ans = max(ans, dq[c] + (ss1[g1] + ss2[g2]) * (sum_ - (ss1[g1] + ss2[g2])) - sum);
		if ((ss1[g1] + ss2[g2]) * 2 <= sum_)
			g1++;
		else
			g2--;
	}
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

Main.c: In function 'append':
Main.c:16:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   16 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
Main.c: In function 'brute':
Main.c:65:22: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   65 |   while (g < (1 << h + 1))
      |                    ~~^~~
Main.c:66:47: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   66 |    ss_[g++] = g2 == (1 << h) || g1 < (1 << h) && ss[g1] < ss[g2] + ww[h] ? ss[g1++] : ss[g2++] + ww[h];
      |                                 ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
Main.c:67:27: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   67 |   memcpy(ss, ss_, (1 << h + 1) * sizeof *ss_);
      |                         ~~^~~
Main.c: In function 'main':
Main.c:76:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
Main.c:80:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |   scanf("%d", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~
Main.c:82:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   82 |   scanf("%d", &i), i--;
      |   ^~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 5 / 5
• Subtask 5: 5 / 5