Submission #914562

#	Time	Username	Problem	Language	Result	Execution time	Memory
914562		Ghetto	Hacker (BOI15_hac)	C++17	100 / 100	261 ms	12364 KiB

hac

#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 5e5 + 5;

int n;
int arr[MAX_N];

int segtree[4 * MAX_N];
void update(int i, int x, int u = 1, int lo = 1, int hi = n) {
    if (lo == hi) {
        segtree[u] = x;
        return;
    }

    int mid = (lo + hi) / 2;
    if (i <= mid)
        update(i, x, 2 * u, lo, mid);
    else
        update(i, x, 2 * u + 1, mid + 1, hi);
    segtree[u] = max(segtree[2 * u], segtree[2 * u + 1]);
}
int query(int l, int r, int u = 1, int lo = 1, int hi = n) {
    if (l <= lo && hi <= r)
        return segtree[u];
    
    int mid = (lo + hi) / 2, ans = 0; // arr[i] >= 1
    if (l <= mid) 
        ans = max(ans, query(l, r, 2 * u, lo, mid));
    if (r > mid)
        ans = max(ans, query(l, r, 2 * u + 1, mid + 1, hi));
    return ans;
}

int subarray_sum[MAX_N];
int tot_sum;
void precomp() {
    int s = n / 2;

    for (int i = 1; i <= s; i++)
        subarray_sum[1] += arr[i];
    for (int i = 2; i <= n; i++) {
        int j = i + s - 1;
        if (j > n) 
            j -= n;
        subarray_sum[i] = subarray_sum[i - 1] - arr[i - 1] + arr[j];
        // cout << subarray_sum[i] << " ";
    }
    for (int i = 1; i <= n; i++)
        update(i, subarray_sum[i]);
    
    for (int i = 1; i <= n; i++)
        tot_sum += arr[i];
}

int main() {
    // freopen("hacker.in", "r", stdin);

    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> arr[i];
    
    precomp();
    
    int s = n / 2;
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        int j = i - s;
        if (j >= 1)
            ans = max(ans, tot_sum - max(query(i + 1, n), query(1, j)));
        else {
            j += n;
            ans = max(ans, tot_sum - query(i + 1, j));
        }
    }
    cout << ans << '\n';
}

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 40 / 40