题解 | 牛牛与切割机

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 3;
using ll = long long;
ll a[N],p[N],b[N];
int main()
{
    int n;cin >> n;
    for(int i = 1;i <= n;i++)cin >> a[i];
    for(int i = 1;i <= n;i++)
    {
        int r = n - i + 1;
        p[i] = p[i - 1] + a[i];//前缀和
        b[r] = b[r + 1] + a[r];//后缀和
    }
    ll ans = 2e18;
    for(int i = 1;i < n;i++)//分成两部分，i<n
    {
        ans = min(ans,p[i] * b[i + 1]);
    }
    cout << ans << '\n';
    return 0;
}