Submission #1258831

#	Time	Username	Problem	Language	Result	Execution time	Memory
1258831		phtung	Feast (NOI19_feast)	C++20	100 / 100	259 ms	21572 KiB

feast

#include <bits/stdc++.h>

using namespace std;

#define name "IO"
#define int long long
const long long INF = (long long)1e18;
const int MAXN = 3e5 + 5;
const long double EPS = 1e-6;

int n, k, a[MAXN];
pair<long double,int> dp[MAXN][2]; 

bool check(long double lambda) {
    dp[0][0] = {0, 0};
    dp[0][1] = {-INF, 0};

    for (int i = 1; i <= n; i++) {
        dp[i][0] = max(dp[i-1][0], dp[i-1][1]);

        auto v1 = make_pair(dp[i-1][1].first + a[i], dp[i-1][1].second);
        auto v2 = make_pair(dp[i-1][0].first + a[i] - lambda, dp[i-1][0].second + 1);
        dp[i][1] = max(v1, v2);
    }
    return max(dp[n][0], dp[n][1]).second >= k;
}

void solve() {
    cin >> n >> k;
    for (int i = 1; i <= n; i++) cin >> a[i];

    long double low = 0, high = 1e12;
    while (high - low > EPS) {
        long double mid = (low + high) / 2;
        if (check(mid)) low = mid;
        else high = mid;
    }

    long double lambda = low;
    check(lambda); 
    auto best = max(dp[n][0], dp[n][1]);
    cout << (long long)round(lambda * k + best.first) << "\n";
}

signed main()
{
    if (fopen (name".INP", "r"))
    {
        freopen (name".INP", "r", stdin);
        freopen (name".OUT", "w", stdout);
    }

    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    clock_t start = clock(); 

    int t = 1;

    while(t--) solve(); 

    std::cerr << "Time: " << clock() - start << "ms\n";

    return 0; 

}

Compilation message (stderr)

feast.cpp: In function 'int main()':
feast.cpp:49:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |         freopen (name".INP", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
feast.cpp:50:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen (name".OUT", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• 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