Submission #949042

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
949042	2024-03-18T20:45:55 Z	rainboy	초록색 삼각형 (YDX13_green)	C	1 / 1	629 ms	600 KB

C

#include <stdio.h>

#define N	2000

typedef __int128_t L;

unsigned int Z = 12345;

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

int xx[N], yy[N];

long long cross2(int i, int j) {
	return (long long) xx[i] * yy[j] - (long long) xx[j] * yy[i];
}

long long cross(int i, int j, int k) {
	return (long long) (xx[j] - xx[i]) * (yy[k] - yy[i]) - (long long) (xx[k] - xx[i]) * (yy[j] - yy[i]);
}

int o;

int compare(int i, int j) {
	int sgni, sgnj;
	long long c;

	sgni = xx[i] < xx[o] || xx[i] == xx[o] && yy[i] < yy[o] ? -1 : 1;
	sgnj = xx[j] < xx[o] || xx[j] == xx[o] && yy[j] < yy[o] ? -1 : 1;
	if (sgni != sgnj)
		return sgni - sgnj;
	c = cross(o, i, j);
	return c == 0 ? 0 : (c < 0 ? -1 : 1);
}

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

		while (j < k) {
			int c = compare(jj[j], j_);

			if (c == 0)
				j++;
			else if (c < 0) {
				tmp = jj[i], jj[i] = jj[j], jj[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = jj[j], jj[j] = jj[k], jj[k] = tmp;
			}
		}
		sort(jj, l, i);
		l = k;
	}
}

int main() {
	static int jj[N];
	int n, n_, i, j, k;
	L ans;

	scanf("%d", &n);
	if (n <= 2) {
		printf("0\n");
		return 0;
	}
	for (i = 0; i < n; i++)
		scanf("%d%d", &xx[i], &yy[i]);
	ans = 0;
	for (i = 0; i < n; i++) {
		n_ = 0;
		for (j = 0; j < n; j++)
			if (j != i)
				jj[n_++] = j;
		o = i, sort(jj, 0, n_);
		for (j = 0, k = 0; j < n_; j++) {
			while (k < j + n_ && cross(o, jj[j % n_], jj[k % n_]) <= 0)
				k++;
			ans += (L) (k - j - 1) * cross2(jj[j % n_], o);
		}
	}
	printf("%.12f\n", (double) ans / 2 / ((long long) n * (n - 1) * (n - 2) / 6));
	return 0;
}

Compilation message

C.c: In function 'compare':
C.c:29:41: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   29 |  sgni = xx[i] < xx[o] || xx[i] == xx[o] && yy[i] < yy[o] ? -1 : 1;
      |                          ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
C.c:30:41: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   30 |  sgnj = xx[j] < xx[o] || xx[j] == xx[o] && yy[j] < yy[o] ? -1 : 1;
      |                          ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
C.c: In function 'main':
C.c:64:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
C.c:70:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |   scanf("%d%d", &xx[i], &yy[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1

1.0 / 1.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	0 ms	344 KB	Output is correct
2	Correct	0 ms	344 KB	Output is correct
3	Correct	0 ms	348 KB	Output is correct
4	Correct	0 ms	348 KB	Output is correct
5	Correct	1 ms	600 KB	Output is correct
6	Correct	0 ms	348 KB	Output is correct
7	Correct	0 ms	348 KB	Output is correct
8	Correct	0 ms	348 KB	Output is correct
9	Correct	0 ms	348 KB	Output is correct
10	Correct	0 ms	348 KB	Output is correct
11	Correct	106 ms	348 KB	Output is correct
12	Correct	204 ms	348 KB	Output is correct
13	Correct	130 ms	344 KB	Output is correct
14	Correct	536 ms	596 KB	Output is correct
15	Correct	51 ms	348 KB	Output is correct
16	Correct	549 ms	596 KB	Output is correct
17	Correct	30 ms	348 KB	Output is correct
18	Correct	81 ms	416 KB	Output is correct
19	Correct	133 ms	348 KB	Output is correct
20	Correct	0 ms	348 KB	Output is correct
21	Correct	598 ms	456 KB	Output is correct
22	Correct	597 ms	592 KB	Output is correct
23	Correct	595 ms	452 KB	Output is correct
24	Correct	629 ms	456 KB	Output is correct
25	Correct	592 ms	592 KB	Output is correct
26	Correct	595 ms	452 KB	Output is correct
27	Correct	592 ms	344 KB	Output is correct
28	Correct	614 ms	456 KB	Output is correct
29	Correct	594 ms	456 KB	Output is correct
30	Correct	600 ms	596 KB	Output is correct
31	Correct	0 ms	344 KB	Output is correct