Submission #439945

#	Time	Username	Problem	Language	Result	Execution time	Memory
439945		dongliu0426	Feast (NOI19_feast)	C++14	100 / 100	820 ms	23296 KiB

feast

#include <bits/stdc++.h>
using namespace std;

#define N	300000
#define INF	0x3f3f3f3f3f3f3f3f

int n, k, a[N + 1];
pair<long double, int> dp[N + 1][2];

template<class T, class U> T lastTrue(T lo, T hi, U f) {
	assert(lo <= hi); --lo; /* assuming f is decreasing */
	while (lo < hi) { /* find last index such that f is true */
		T mid = lo + (hi - lo + 1) / 2;
		f(mid) ? lo = mid : hi = mid - 1;
	} return lo;
}

int main() {
	scanf("%d%d", &n, &k);
	for (int i = 1; i <= n; ++i)
		scanf("%d", a + i);
	auto check = [&](long double penalty) {
		dp[0][0] = {0, 0}, dp[0][1] = {-INF, 0};
		for (int i = 1; i <= n; ++i) {
			pair<long double, int> last = max(dp[i - 1][0], dp[i - 1][1]);
			dp[i][0] = max(make_pair(last.first - penalty, last.second + 1), last);
			dp[i][1] = max(make_pair(dp[i - 1][1].first + a[i], dp[i - 1][1].second),
				make_pair(dp[i - 1][0].first + a[i] - penalty, dp[i - 1][0].second + 1));
		}
		return max(dp[n][0], dp[n][1]).second >= k;
	};
	long double lower = 0, upper = INF;
	for (int it = 0; it < 100; ++it) {
		long double mid = (lower + upper) / 2;
		if (check(mid)) {
			lower = mid;
		} else {
			upper = mid;
		}
	}
	long double penalty = lower;
	check(penalty);
	printf("%lld\n", (long long) round(penalty * k + max(dp[n][0], dp[n][1]).first));
}

Compilation message (stderr)

feast.cpp: In function 'int main()':
feast.cpp:19:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |  scanf("%d%d", &n, &k);
      |  ~~~~~^~~~~~~~~~~~~~~~
feast.cpp:21:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |   scanf("%d", a + i);
      |   ~~~~~^~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 18 / 18
• Subtask 4: 10 / 10
• Subtask 5: 11 / 11
• Subtask 6: 20 / 20
• Subtask 7: 29 / 29