d.cpp (wa)

#include <algorithm>
#include <iostream>
#include <unordered_map>
#include <vector>

using namespace std;

#define ull unsigned long long
unordered_map<string, ull> cache;
ull dp(const vector<ull>& prefix, ull l, ull r) {
    if (l >= r) {
        return 0;
    }
    string key = l + "-" + r;
    if (cache.find(key) != cache.end()) {
        return cache[key];
    }
    ull current = 0;
    for (ull i = l; i < r; ++i) {
        ull scoreL = prefix[i];
        if (l > 0) {
            scoreL -= prefix[l - 1];
        }
        ull scoreR = prefix[r] - prefix[i];
        if (scoreL > scoreR) {
            current = max(current, scoreR + dp(prefix, i + 1, r));
        } else if (scoreL < scoreR) {
            current = max(current, scoreL + dp(prefix, l, i));
        } else {
            ull tempL = scoreL + dp(prefix, i + 1, r);
            ull tempR = scoreR + dp(prefix, l, i);
            current = max(current, max(tempL, tempR));
        }
    }
    cache[key] = current;
    return current;
}

int main() {
    ull n;
    cin >> n;
    vector<ull> N(n);
    for (ull i = 0; i < n; ++i) {
        cin >> N[i];
    }
    vector<ull> prefix(N.size());
    prefix[0] = N[0];
    for (size_t i = 1; i < N.size(); ++i) {
        prefix[i] = N[i] + prefix[i - 1];
    }
    cout << dp(prefix, 0, prefix.size() - 1) << "\n";
    return 0;
}