Submission #723559

#	Time	Username	Problem	Language	Result	Execution time	Memory
723559		dxz05	Hacker (BOI15_hac)	C++17	100 / 100	200 ms	10296 KiB

hac

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define MP make_pair
const int N = 500500;

int n;
int a[N], p[N];
int get_sum(int l, int r){
    if (l <= r){
        return p[r] - (l == 0 ? 0 : p[l - 1]);
    } else {
        return p[r] + (p[n - 1] - p[l - 1]);
    }
}

int t[4 * N];
int val[N];

void build(int v, int tl, int tr){
    if (tl == tr){
        t[v] = val[tl];
        return;
    }
    int tm = (tl + tr) >> 1;
    build(v << 1, tl, tm);
    build(v << 1 | 1, tm + 1, tr);
    t[v] = max(t[v << 1], t[v << 1 | 1]);
}

int get(int v, int tl, int tr, int l, int r){
    if (l <= tl && tr <= r) return t[v];
    if (tl > r || tr < l) return 0;
    int tm = (tl + tr) >> 1;
    return max(get(v << 1, tl, tm, l, r), get(v << 1 | 1, tm + 1, tr, l, r));
}

int get(int l, int r){
    if (l <= r){
        return get(1, 0, n - 1, l, r);
    } else {
        return max(get(1, 0, n - 1, l, n - 1), get(1, 0, n - 1, 0, r));
    }
}

void solve(){
    cin >> n;

    for (int i = 0; i < n; i++){
        cin >> a[i];
        p[i] = a[i] + (i > 0 ? p[i - 1] : 0);
    }

    for (int i = 0; i < n; i++){
        int l = (i - n / 2 + 1 + n) % n;
        val[i] = get_sum(l, i);
    }

    build(1, 0, n - 1);

    int ans = 0;
    for (int i = 0; i < n; i++){
        int l = (i + n / 2) % n, r = (i + n - 1) % n;
        int mx = get(l, r);
        ans = max(ans, get_sum(0, n - 1) - mx);
    }

    cout << ans << endl;

}

int main() {
    ios_base::sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    solve();

    return 0;
}

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