Submission #502819

#	Time	Username	Problem	Language	Result	Execution time	Memory
502819		rainboy	Tortoise (CEOI21_tortoise)	C11	0 / 100	1 ms	332 KiB

tortoise

/* https://hsin.hr/ceoi/competition/ceoi2021_day2_editorial.pdf */
#include <stdio.h>

#define N	500000
#define INF	0x3f3f3f3f

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

unsigned int X = 12345;

int rand_() {
	return (X *= 3) >> 1;
}

int tt[N], dd[N];

void sort(int *ii, int l, int r) {
	while (l < r) {
		int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;

		while (j < k)
			if (dd[ii[j]] == dd[i_])
				j++;
			else if (dd[ii[j]] < dd[i_]) {
				tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
			}
		sort(ii, l, i);
		l = k;
	}
}

int check(int *ss, int *kk, int n) {
	int i, s;

	for (i = 0, s = 0; i < n; i++) {
		s += ss[i];
		if (kk[i] > 0 && s < 0)
			return 0;
	}
	return 1;
}

int main() {
	static int ii[N], aa[N], ll[N], rr[N], dd[N], pp[N], ss[N], kk[N];
	int n, n_, i, j, ans;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		scanf("%d", &aa[i]);
	for (i = 0; i < n; i++)
		ll[i] = aa[i] == -1 ? i : (i == 0 ? -INF : ll[i - 1]);
	for (i = n - 1; i >= 0; i--)
		rr[i] = aa[i] == -1 ? i : (i + 1 == n ? INF : rr[i + 1]);
	n_ = 0;
	for (i = 0; i < n; i++)
		if (aa[i] > 0) {
			if (i - ll[i] <= rr[i] - i)
				tt[i] = -1, dd[i] = i - ll[i];
			else
				tt[i] = 1, dd[i] = rr[i] - i;
			ii[n_++] = i;
		}
	ans = 0;
	for (i = 0; i < n; i++)
		if (aa[i] > 0)
			ans += aa[i];
	for (j = 0; j < n; j++)
		if (aa[j] == -1) {
			i = j - 1;
			while (i >= 0 && aa[i] == 0)
				i--;
			if (i >= 0 && aa[i] > 0)
				pp[j] = i, kk[i]++, ans--;
			else
				pp[j] = -1;
		}
	sort(ii, 0, n_);
	for (i = 1; i < n; i++)
		ss[i] = 1;
	for (i = 0; i < n; i++) {
		int i_ = ii[i], r = rr[i_], p;

		while (kk[i_] <= aa[i_]) {
			p = r == INF ? INF : pp[r];
			if (tt[i_] == -1) {
				if (kk[i_] == aa[i_])
					break;
				if (kk[i_]++ == 0) {
					if (i_ + 1 < n)
						ss[i_ + 1] -= dd[i_] * 2;
				} else
					ss[i_] -= dd[i_] * 2;
				if (check(ss, kk, n))
					ans--;
				else {
					if (--kk[i_] == 0) {
						if (i_ + 1 < n)
							ss[i_ + 1] += dd[i_] * 2;
					} else
						ss[i_] += dd[i_] * 2;
					break;
				}
			} else {
				if (i_ < p)
					break;
				while (p >= 0 && kk[p] == aa[p])
					p--;
				if (p < 0 || aa[p] == -1)
					break;
				kk[p]++, ss[i_] -= dd[i_] * 2;
				if (check(ss, kk, n))
					pp[r] = p, ans--;
				else {
					kk[p]--, ss[i_] += dd[i_] * 2;
					break;
				}
			}
		}
	}
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

tortoise.c: In function 'main':
tortoise.c:52:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
tortoise.c:54:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |   scanf("%d", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 10
• Subtask 3: 0 / 30
• Subtask 4: 0 / 25
• Subtask 5: 0 / 27