mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-25 19:12:02 +00:00
81 lines
2.0 KiB
C++
81 lines
2.0 KiB
C++
#include <iostream>
|
|
#include <algorithm>
|
|
#include <limits>
|
|
|
|
using std::cin;
|
|
using std::cout;
|
|
const char endl = '\n';
|
|
|
|
const int N = 2e5 + 5;
|
|
|
|
int n, a[N];
|
|
bool flag = true;
|
|
long long sum, s_max[N], s_min[N], f_max[N], f_min[N], g_max[N], g_min[N], ans;
|
|
|
|
int main() {
|
|
std::ios::sync_with_stdio(false);
|
|
cin.tie(nullptr);
|
|
|
|
cin >> n;
|
|
|
|
for (int i = 1; i <= n; i++) {
|
|
cin >> a[i];
|
|
|
|
sum += a[i];
|
|
flag &= a[i] < 0;
|
|
}
|
|
|
|
if (flag) {
|
|
std::sort(a + 1, a + 1 + n);
|
|
|
|
cout << a[n] + a[n - 1] << endl;
|
|
|
|
exit(0);
|
|
}
|
|
|
|
ans = std::numeric_limits<int>::min();
|
|
std::fill_n(s_max, N, std::numeric_limits<int>::min());
|
|
std::fill_n(s_min, N, std::numeric_limits<int>::max());
|
|
std::fill_n(f_max, N, std::numeric_limits<int>::min());
|
|
std::fill_n(f_min, N, std::numeric_limits<int>::max());
|
|
std::fill_n(g_max, N, std::numeric_limits<int>::min());
|
|
std::fill_n(g_min, N, std::numeric_limits<int>::max());
|
|
|
|
for (int i = 1; i <= n; i++) {
|
|
s_max[i] = std::max(s_max[i - 1] + a[i], static_cast<long long>(a[i]));
|
|
s_min[i] = std::min(s_min[i - 1] + a[i], static_cast<long long>(a[i]));
|
|
|
|
f_max[i] = std::max(f_max[i - 1], s_max[i]);
|
|
f_min[i] = std::min(f_min[i - 1], s_min[i]);
|
|
}
|
|
|
|
std::fill_n(s_max, N, std::numeric_limits<int>::min());
|
|
std::fill_n(s_min, N, std::numeric_limits<int>::max());
|
|
|
|
for (int i = n; i; i--) {
|
|
s_max[i] = std::max(s_max[i + 1] + a[i], static_cast<long long>(a[i]));
|
|
s_min[i] = std::min(s_min[i + 1] + a[i], static_cast<long long>(a[i]));
|
|
|
|
g_max[i] = std::max(g_max[i + 1], s_min[i]);
|
|
g_min[i] = std::min(g_min[i + 1], s_min[i]);
|
|
}
|
|
|
|
std::cerr << ans << endl;
|
|
|
|
// 不跨环
|
|
for (int i = 1; i < n; i++) {
|
|
ans = std::max(ans, f_max[i] + g_max[i + 1]);
|
|
}
|
|
|
|
std::cerr << ans << endl;
|
|
|
|
// 跨环
|
|
for (int i = 1; i < n; i++) {
|
|
ans = std::max(ans, sum - (f_min[i] + g_min[i + 1]));
|
|
}
|
|
|
|
cout << ans << endl;
|
|
|
|
return 0;
|
|
}
|