Submission #768246

#	Time	Username	Problem	Language	Result	Execution time	Memory
768246		rainboy	Hard route (IZhO17_road)	C11	100 / 100	372 ms	54356 KiB

road

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

#define N	500000

int *ej[N], eo[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;
}

long long x_, y_;

int dd[N], kk[N];

void dfs(int p, int i, int r) {
	int o;

	dd[i] = 0, kk[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			int d, k;
			long long x, y;

			dfs(i, j, r + 1);
			d = dd[j] + 1, k = kk[j];
			if (dd[i] > 0) {
				x = (long long) (dd[i] + d) * r, y = (long long) kk[i] * kk[j];
				if (x_ < x)
					x_ = x, y_ = 0;
				if (x_ == x)
					y_ += y;
			}
			if (dd[i] < d)
				dd[i] = d, kk[i] = 0;
			if (dd[i] == d)
				kk[i] += k;
		}
	}
}

int main() {
	static int qu[N], qu_[N];
	int n, n_, cnt, cnt_, r, h, i, j, d, d_, k, k_, k1, o;
	long long x, y;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (h = 0; h < n - 1; h++) {
		scanf("%d%d", &i, &j), i--, j--;
		append(i, j), append(j, i);
	}
	memcpy(eo_, eo, n * sizeof *eo);
	cnt = 0;
	for (i = 0; i < n; i++)
		if (eo[i] == 1)
			qu[cnt++] = i;
	n_ = n, r = 0;
	while (n_ >= 3) {
		cnt_ = 0;
		for (h = 0; h < cnt; h++) {
			i = qu[h];
			for (o = eo[i]; o--; ) {
				j = ej[i][o];
				if (--eo_[j] == 1)
					qu_[cnt_++] = j;
			}
		}
		n_ -= cnt, r++;
		memcpy(qu, qu_, (cnt = cnt_) * sizeof *qu_);
	}
	x_ = 0, y_ = 0;
	if (n_ == 1) {
		i = qu[0], cnt = 0;
		for (o = eo[i]; o--; ) {
			j = ej[i][o];
			dfs(i, j, r + 1);
			d = dd[j] + 1;
			if (d == r)
				cnt++;
		}
		if (cnt == 2) {
			d_ = 0, k_ = 0, k1 = 0;
			for (o = eo[i]; o--; ) {
				j = ej[i][o], d = dd[j] + 1, k = kk[j];
				if (d == r)
					k1 += kk[j];
				else {
					if (d_ < d)
						d_ = d, k_ = 0;
					if (d_ == d)
						k_ += k;
				}
			}
			if (d_ > 0) {
				x = (long long) (r + d_) * r, y = (long long) k1 * k_;
				if (x_ < x)
					x_ = x, y_ = 0;
				if (x_ == x)
					y_ += y;
			}
		} else {
			k1 = 0, y = 0;
			for (o = eo[i]; o--; ) {
				j = ej[i][o], d = dd[j] + 1, k = kk[j];
				if (d == r)
					k1 += kk[j], y -= (long long) kk[j] * kk[j];
			}
			y += (long long) k1 * k1, y /= 2;
			x = (long long) (r + r) * r;
			if (x_ < x)
				x_ = x, y_ = 0;
			if (x_ == x)
				y_ += y;
		}
	} else {
		i = qu[0], j = qu[1];
		dfs(i, j, r + 1), dfs(j, i, r + 1);
	}
	if (x_ == 0)
		y_ = 1;
	printf("%lld %lld\n", x_, y_);
	return 0;
}

Compilation message (stderr)

road.c: In function 'append':
road.c:12:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   12 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
road.c: In function 'main':
road.c:54:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
road.c:58:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 19 / 19
• Subtask 2: 33 / 33
• Subtask 3: 48 / 48