Submission #741224

#	Time	Username	Problem	Language	Result	Execution time	Memory
741224		rainboy	Count Squares (CEOI19_countsquares)	C11	100 / 100	278 ms	9104 KiB

countsquares

#include <stdio.h>

#define N	1500
#define N2	(N * (N - 1) / 2)

unsigned int X = 12345;

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

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

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

int main() {
	static int aa[N], bb[N], aa_[N2], bb_[N2];
	int n, n_, m, m_, i, i_, i1, i2, j, j_, j1, j2;
	long long ans;

	scanf("%d%d", &n, &m);
	for (i = 0; i < n; i++)
		scanf("%d", &aa[i]);
	for (j = 0; j < m; j++)
		scanf("%d", &bb[j]);
	n_ = 0;
	for (i1 = 0; i1 < n; i1++)
		for (i2 = i1 + 1; i2 < n; i2++)
			aa_[n_++] = aa[i2] - aa[i1];
	sort(aa_, 0, n_);
	m_ = 0;
	for (j1 = 0; j1 < m; j1++)
		for (j2 = j1 + 1; j2 < m; j2++)
			bb_[m_++] = bb[j2] - bb[j1];
	sort(bb_, 0, m_);
	i = 0, j = 0, ans = 0;
	while (i < n_ && j < m_)
		if (aa_[i] < bb_[j])
			i++;
		else if (aa_[i] > bb_[j])
			j++;
		else {
			i_ = i + 1;
			while (i_ < n_ && aa_[i_] == aa_[i])
				i_++;
			j_ = j + 1;
			while (j_ < m_ && bb_[j_] == bb_[j])
				j_++;
			ans += (long long) (i_ - i) * (j_ - j);
			i = i_, j = j_;
		}
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

countsquares.c: In function 'main':
countsquares.c:36:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |  scanf("%d%d", &n, &m);
      |  ^~~~~~~~~~~~~~~~~~~~~
countsquares.c:38:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |   scanf("%d", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~
countsquares.c:40:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |   scanf("%d", &bb[j]);
      |   ^~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 40 / 40
• Subtask 3: 53 / 53