Submission #719176

#	Time	Username	Problem	Language	Result	Execution time	Memory
719176		rainboy	Seesaw (JOI22_seesaw)	C11	100 / 100	97 ms	8460 KiB

seesaw

#include <stdio.h>

#define N	200000

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

unsigned int X = 12345;

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

double xx[N], yy[N];

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

		while (j < k)
			if (xx[hh[j]] == xx[h])
				j++;
			else if (xx[hh[j]] < xx[h]) {
				tmp = hh[i], hh[i] = hh[j], hh[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = hh[j], hh[j] = hh[k], hh[k] = tmp;
			}
		sort(hh, l, i);
		l = k;
	}
}

int main() {
	static int aa[N], hh[N];
	static long long ss[N + 1];
	int n, m, h, i, k, lower, upper;
	double y, ans;

	scanf("%d", &n);
	ss[0] = 0;
	for (i = 0; i < n; i++) {
		scanf("%d", &aa[i]);
		ss[i + 1] = ss[i] + aa[i];
	}
	m = 0;
	for (k = 1; k < n; k++) {
		lower = 0, upper = n - k + 1;
		while (upper - lower > 1) {
			i = (lower + upper) / 2;
			if ((double) (ss[i + k] - ss[i]) / k <= (double) ss[n] / n)
				lower = i;
			else
				upper = i;
		}
		i = lower;
		if ((double) (ss[i + k] - ss[i]) / k == (double) ss[n] / n)
			continue;
		xx[m] = (double) (ss[i + k] - ss[i]) / k, yy[m] = (double) (ss[i + 1 + k] - ss[i + 1]) / k, m++;
	}
	if (m == 0) {
		printf("0\n");
		return 0;
	}
	for (h = 0; h < m; h++)
		hh[h] = h;
	sort(hh, 0, m);
	y = (double) ss[n] / n;
	ans = y - xx[hh[0]];
	for (h = 0; h < m; h++) {
		y = max(y, yy[hh[h]]);
		ans = min(ans, y - (h + 1 < m ? xx[hh[h + 1]] : (double) ss[n] / n));
	}
	printf("%.12f\n", ans);
	return 0;
}

Compilation message (stderr)

seesaw.c: In function 'main':
seesaw.c:41:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   41 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
seesaw.c:44:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 |   scanf("%d", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 33 / 33
• Subtask 3: 33 / 33
• Subtask 4: 33 / 33