Submission #833782

#	Time	Username	Problem	Language	Result	Execution time	Memory
833782		rainboy	Discharging (NOI20_discharging)	C11	100 / 100	100 ms	18364 KiB

Discharging

#include <stdio.h>

#define N	1000000

typedef long double ld;

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

int ii[N]; long long dp[N + 1];

ld cross(int i, int j, int k) {
	return (ld) (ii[j] - ii[i]) * (dp[k] - dp[i]) - (ld) (ii[k] - ii[i]) * (dp[j] - dp[i]);
}

long long eval(int i, int a) {
	return dp[i] - (long long) ii[i] * a;
}

int main() {
	static int aa[N], qu[N];
	int n, n_, cnt, h, i, i_, a;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		scanf("%d", &aa[i]);
	n_ = 0;
	for (i = 0, i_ = -1; i < n; i++)
		if (i_ == -1 || aa[i_] < aa[i])
			ii[n_++] = i, i_ = i;
	cnt = 0;
	for (h = 0, i = 0; i <= n_; i++) {
		if (i == 0)
			dp[i] = 0;
		else {
			a = aa[ii[i - 1]];
			while (h + 1 < cnt && eval(qu[h], a) >= eval(qu[h + 1], a))
				h++;
			dp[i] = eval(qu[h], a) + (long long) n * a;
		}
		if (i < n_) {
			while (cnt >= 2 && cross(qu[cnt - 2], qu[cnt - 1], i) <= 0)
				cnt--;
			qu[cnt++] = i;
			h = min(h, cnt - 1);
		}
	}
	printf("%lld\n", dp[n_]);
	return 0;
}

Compilation message (stderr)

Discharging.c: In function 'main':
Discharging.c:23:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
Discharging.c:25:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |   scanf("%d", &aa[i]);
      |   ^~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 13 / 13
• Subtask 3: 25 / 25
• Subtask 4: 11 / 11
• Subtask 5: 14 / 14
• Subtask 6: 28 / 28