Submission #831769

#	Time	Username	Problem	Language	Result	Execution time	Memory
831769		rainboy	Mountains (NOI20_mountains)	C11	100 / 100	93 ms	10648 KiB

Mountains

#include <stdio.h>

#define N	300000

unsigned int X = 12345;

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

long long aa[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 (aa[ii[j]] == aa[i_])
				j++;
			else if (aa[ii[j]] < aa[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 ft[N];

void update(int i, int n) {
	while (i < n) {
		ft[i]++;
		i |= i + 1;
	}
}

int query(int i) {
	int x = 0;

	while (i >= 0) {
		x += ft[i];
		i &= i + 1, i--;
	}
	return x;
}

int main() {
	static int ii[N];
	int n, h, i, j, k;
	long long ans;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		scanf("%lld", &aa[i]);
	for (i = 0; i < n; i++)
		ii[i] = i;
	sort(ii, 0, n);
	ans = 0;
	for (i = 0; i < n; i = j) {
		j = i + 1;
		while (j < n && aa[ii[j]] == aa[ii[i]])
			j++;
		for (h = i; h < j; h++) {
			k = query(ii[h]);
			ans += (long long) k * (i - k);
		}
		for (h = i; h < j; h++)
			update(ii[h], n);
	}
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

Mountains.c: In function 'main':
Mountains.c:56:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
Mountains.c:58:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |   scanf("%lld", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12