Submission #924804

#	Time	Username	Problem	Language	Result	Execution time	Memory
924804		rainboy	트리 (KOI16_tree)	C11	100 / 100	160 ms	34380 KiB

tree

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

#define N	200000

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 dd[N], pp[N], qq[N], ta[N], tb[N];

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

	dd[i] = d;
	s = 1, k_ = 0, j_ = -1;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o], k = dfs1(j, d + 1);

		s += k;
		if (k_ < k)
			k_ = k, j_ = j;
	}
	qq[i] = j_;
	return s;
}

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

	ta[i] = time++;
	j_ = qq[i], qq[i] = q;
	if (j_ != -1)
		dfs2(j_, q);
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != j_)
			dfs2(j, j);
	}
	tb[i] = time;
}

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 ft[N];

void update(int i, int n, int x) {
	while (i < n) {
		ft[i] += x;
		i |= i + 1;
	}
}

int query(int i) {
	int x = 0;

	while (i >= 0) {
		x += ft[i];
		i &= i + 1, i--;
	}
	return x;
}

int main() {
	int n, q, i;

	scanf("%d%d", &n, &q);
	for (i = 0; i < n; i++)
		ej[i] = (int *) malloc(2 * sizeof *ej[i]);
	for (i = 1; i < n; i++) {
		scanf("%d", &pp[i]), pp[i]--;
		append(pp[i], i);
	}
	dfs1(0, 0);
	dfs2(0, 0);
	while (q--) {
		int i, j, upd, yes;

		scanf("%d%d%d", &i, &j, &upd), i--, j--;
		yes = query(ta[i]) + query(ta[j]) - query(ta[lca(i, j)]) * 2 == 0;
		printf(yes ? "YES\n" : "NO\n");
		if (upd) {
			if (!yes)
				i = j;
			update(ta[i], n, 1), update(tb[i], n, -1);
		}
	}
	return 0;
}

Compilation message (stderr)

tree.c: In function 'append':
tree.c:11:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   11 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
tree.c: In function 'main':
tree.c:83:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   83 |  scanf("%d%d", &n, &q);
      |  ^~~~~~~~~~~~~~~~~~~~~
tree.c:87:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |   scanf("%d", &pp[i]), pp[i]--;
      |   ^~~~~~~~~~~~~~~~~~~
tree.c:95:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   95 |   scanf("%d%d%d", &i, &j, &upd), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 13 / 13
• Subtask 3: 14 / 14
• Subtask 4: 19 / 19
• Subtask 5: 45 / 45