Submission #500978

#	Time	Username	Problem	Language	Result	Execution time	Memory
500978		rainboy	Wells (CEOI21_wells)	C11	0 / 100	1 ms	332 KiB

wells

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

#define N	200

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

int *ej[N], eo[N], n, k;

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 dd1[N], dd2[N];

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

	dd1[i] = 1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			dfs1(i, j);
			dd1[i] = max(dd1[i], dd1[j] + 1);
		}
	}
}

void dfs2(int p, int i, int d) {
	int o, d1, d2, j1;

	d1 = d2 = 0, j1 = -1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p) {
			if (d1 < dd1[j])
				d2 = d1, d1 = dd1[j], j1 = j;
			else if (d2 < dd1[j])
				d2 = dd1[j];
		}
	}
	dd2[i] = d;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p)
			dfs2(i, j, max(d, j == j1 ? d2 : d1) + 1);
	}
}

char dp[N][N + 1], dq[N + 1]; int ll[N], rr[N];

void dfs3(int p, int i) {
	static int jj[N], dd[N + 1];
	int m, o, h, di, dj, d;

	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p)
			dfs3(i, j);
	}
	m = 0;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p)
			jj[m++] = j;
	}
	dd[m] = dd2[i];
	for (h = m - 1; h >= 0; h--) {
		int j = jj[h];

		dd[h] = max(dd[h + 1], dd1[j]);
	}
	ll[i] = max(k - 1 - dd[0], 0), rr[i] = max(ll[i], 1);
	if (ll[i] >= rr[i])
		dp[i][ll[i]] = 1;
	else
		dp[i][0] = dp[i][1] = 1;
	for (h = 0; h < m; h++) {
		int j = jj[h], l_, r_;

		memset(dq, 0, (n + 1) * sizeof *dq);
		l_ = max(k - 1 - dd[h + 1], 0), r_ = max(max(rr[i], rr[j] + 1), l_);
		for (di = ll[i]; di <= rr[i]; di++)
			for (dj = ll[j]; dj <= rr[j]; dj++)
				if (dp[i][di] && dp[j][dj]) {
					int good, di_, dj_;

					good = 1;
					if (ll[i] < rr[i] && ll[j] < rr[j])
						for (d = 0; d <= k; d++)
							if (d <= rr[i] && k - d <= rr[j] && (d <= di ? 0 : 1) + (k - d <= dj ? 0 : 1) != 1) {
								good = 0;
								break;
							}
					if (!good)
						continue;
					di_ = max(di, l_), dj_ = max(dj + 1, l_);
					if (di == 0)
						dq[di] = 1;
					else if (min(di_, min(rr[i], rr[j] + 1)) == min(dj_, min(rr[i], rr[j] + 1)))
						dq[min(max(di_, dj_), r_)] = 1;
				}
		memcpy(dp[i], dq, (n + 1) * sizeof *dq);
		ll[i] = l_, rr[i] = r_;
	}
}

int main() {
	int h, i, j;

	scanf("%d%d", &n, &k);
	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);
	dfs2(-1, 0, 0);
	dfs3(-1, 0);
	printf(dp[0][ll[0]] ? "YES\n" : "NO\n");
	printf("0\n");
	return 0;
}

Compilation message (stderr)

wells.c: In function 'append':
wells.c:15:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   15 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
wells.c: In function 'main':
wells.c:122:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |  scanf("%d%d", &n, &k);
      |  ^~~~~~~~~~~~~~~~~~~~~
wells.c:126:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
  126 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 30