Submission #482430

#	Time	Username	Problem	Language	Result	Execution time	Memory
482430		rainboy	Papričice (COCI20_papricice)	C11	110 / 110	163 ms	22892 KiB

papricice

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

#define N	200000

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

int dist(int a, int b, int c) {
	return max(max(a, b), c) - min(min(a, b), c);
}

int *ej[N], eo[N], 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 ta[N], tb[N], c;
int rr[N], sz[N];

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

	ta[i] = time++;
	sz[i] = 1, centroid = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs1(i, j);
			sz[i] += sz[j];
			if (sz[j] * 2 > n)
				centroid = 0;
		}
	}
	if ((n - sz[i]) * 2 > n)
		centroid = 0;
	if (centroid)
		c = i;
	tb[i] = time;
}

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

	rr[i] = r, sz[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs2(i, r, j);
			sz[i] += sz[j];
		}
	}
}

int main() {
	static int rr_[N], dp1[N], dp2[N], dq1[N], dq2[N];
	int h, i, j, s, o, ans;

	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);
	}
	dfs1(-1, 0);
	for (o = eo[c]; o--; ) {
		j = ej[c][o];
		dfs2(c, j, j);
	}
	memset(rr_, -1, n * sizeof *rr_);
	for (i = 0; i < n; i++)
		if (rr_[sz[i]] == -1)
			rr_[sz[i]] = rr[i];
		else if (rr_[sz[i]] != rr[i])
			rr_[sz[i]] = -2;
	for (s = 0; s < n; s++) {
		dp1[s] = s == 0 ? -1 : dp1[s - 1], dp2[s] = s == 0 ? -1 : dp2[s - 1];
		if (rr_[s] != -1) {
			if (dp1[s] == -1 || rr_[dp1[s]] != rr_[s])
				dp2[s] = dp1[s];
			dp1[s] = s;
		}
	}
	for (s = n - 1; s >= 0; s--) {
		dq1[s] = s + 1 == n ? n : dq1[s + 1], dq2[s] = s + 1 == n ? n : dq2[s + 1];
		if (rr_[s] != -1) {
			if (dq1[s] == n || rr_[dq1[s]] != rr_[s])
				dq2[s] = dq1[s];
			dq1[s] = s;
		}
	}
	ans = n + 1;
	for (i = 0; i < n; i++)
		if (i != c) {
			int s, s_;

			if (i != rr[i])
				ans = min(ans, dist(n - sz[rr[i]], sz[rr[i]] - sz[i], sz[i]));
			s = (n - sz[i]) / 2;
			if ((s_ = dp1[s]) != -1 && rr_[s_] != rr[i])
				ans = min(ans, dist(sz[i], s_, n - sz[i] - s_));
			else if ((s_ = dp2[s]) != -1)
				ans = min(ans, dist(sz[i], s_, n - sz[i] - s_));
			if ((s_ = dq1[s]) != n && rr_[s_] != rr[i])
				ans = min(ans, dist(sz[i], s_, n - sz[i] - s_));
			else if ((s_ = dq2[s]) != n)
				ans = min(ans, dist(sz[i], s_, n - sz[i] - s_));
		}
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

papricice.c: In function 'append':
papricice.c:19:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   19 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
papricice.c: In function 'main':
papricice.c:68:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
papricice.c:72:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   72 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 35 / 35
• Subtask 3: 60 / 60