Submission #481343

#	Time	Username	Problem	Language	Result	Execution time	Memory
481343		rainboy	Lampice (COCI19_lampice)	C11	73 / 110	5037 ms	7884 KiB

lampice

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

#define N	50000

int max(int a, int 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;
}

char cc[N + 1]; int d_;

void dfs1(int p1, int i1, int p2, int i2, int d) {
	int o1, o2;

	d_ = max(d_, d);
	for (o1 = eo[i1]; o1--; ) {
		int j1 = ej[i1][o1];

		for (o2 = eo[i2]; o2--; ) {
			int j2 = ej[i2][o2];

			if (j1 != p1 && j2 != p2 && (i1 != i2 || j1 < j2) && cc[j1] == cc[j2])
				dfs1(i1, j1, i2, j2, d + 2);
		}
	}
}

int pp[N], dd[N];

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

	pp[i] = p, dd[i] = d;
	for (o = eo[i]; o--; ) {
		int j = ej[i][o];

		if (j != p)
			dfs2(i, j, d + 1);
	}
}

int manacher(char *cc, int n) {
	static char cc_[N * 2 + 2];
	static int rr[N * 2 + 1];
	int i, o, x, ans;

	for (i = 0; i < n * 2 + 1; i++)
		cc_[i] = i % 2 == 0 ? ' ' : cc[i / 2];
	for (i = 0, o = 0, x = 0; i < n * 2 + 1; i++)
		if (i < x && i + rr[o + o - i] < x)
			rr[i] = rr[o + o - i];
		else {
			o = i, x = max(x, i);
			while (x < n * 2 + 1 && o + o - x >= 0 && cc_[x] == cc_[o + o - x])
				x++;
			rr[i] = x - o;
		}
	ans = 0;
	for (i = 0; i < n * 2 + 1; i++)
		ans = max(ans, rr[i] - 1);
	return ans;
}

int main() {
	static int ii[N - 1], jj[N - 1], qu[N], qu1[N], qu2[N];
	static char cc_[N + 1];
	int n, h, h_, h1, h2, i, j, cnt, cnt1, cnt2;

	scanf("%d%s", &n, cc);
	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--;
		ii[h] = i, jj[h] = j;
		append(i, j), append(j, i);
	}
	if (n <= 3000) {
		for (i = 0; i < n; i++)
			dfs1(-1, i, -1, i, 1);
		for (h = 0; h < n - 1; h++)
			if (cc[ii[h]] == cc[jj[h]])
				dfs1(ii[h], jj[h], jj[h], ii[h], 2);
	} else {
		dfs2(-1, 0, 0);
		cnt = 0;
		for (i = 0; i < n; i++)
			if (eo[i] == 1)
				qu[cnt++] = i;
		for (h = 0; h < cnt; h++)
			for (h_ = h + 1; h_ < cnt; h_++) {
				i = qu[h], j = qu[h_];
				cnt1 = 0, cnt2 = 0;
				while (i != j)
					if (dd[i] > dd[j])
						qu1[cnt1++] = i, i = pp[i];
					else
						qu2[cnt2++] = j, j = pp[j];
				for (h1 = 0; h1 < cnt1; h1++)
					cc_[h1] = cc[qu1[h1]];
				cc_[cnt1] = cc[i];
				for (h2 = 0; h2 < cnt2; h2++)
					cc_[cnt1 + cnt2 - h2] = cc[qu2[h2]];
				cc_[cnt1 + 1 + cnt2] = 0;
				d_ = max(d_, manacher(cc_, cnt1 + 1 + cnt2));
			}
	}
	printf("%d\n", d_);
	return 0;
}

Compilation message (stderr)

lampice.c: In function 'append':
lampice.c:13:23: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   13 |  if (o >= 2 && (o & o - 1) == 0)
      |                     ~~^~~
lampice.c: In function 'main':
lampice.c:77:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 |  scanf("%d%s", &n, cc);
      |  ^~~~~~~~~~~~~~~~~~~~~
lampice.c:81:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |   scanf("%d%d", &i, &j), i--, j--;
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 25 / 25
• Subtask 3: 31 / 31
• Subtask 4: 0 / 37