Educational Codeforces Round 48 (Rated for Div. 2) C. Vasya And The Mushrooms

题目:http://codeforces.com/contest/1016/problem/C
转载:https://blog.csdn.net/qq_40160605/article/details/81432788

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int inf = 0x3f3f3f3f;
const int N = 300005;
int n;
LL a[N];
LL b[N];
LL sum[N],suma[N],sumb[N],sumc[N];

//预处理三种情况
void init()
{
    for(int i = n;i >= 1;--i)
        sum[i] = sum[i + 1] + a[i] + b[i];
    for(int i = n,j = n;i >= 1;--i,++j)
        suma[i] = suma[i + 1] + (i - 1) * a[i] + j * b[i];
    for(int i = n,j = n;i >= 2;--i,++j)
        sumb[i] = sumb[i + 1] + i * b[i] + (j + 1) * a[i];
    sumb[1] = sumb[2] + b[1];
    int tot = 0;
    for(int i = 1;i <= n;++i)
    {
        if(i % 2 == 0){
            sumc[i] += sumc[i - 1];
            sumc[i] += 1LL * tot * b[i];tot++;
            sumc[i] += 1LL * tot * a[i];tot++;
        }
        else{
            sumc[i] += sumc[i - 1];
            sumc[i] += 1LL * tot * a[i]; tot++;
            sumc[i] += 1LL * tot * b[i]; tot++;
        }
    }
}

int main()
{
    while(~scanf("%d",&n))
    {
        memset(sum,0,sizeof(sum));
        memset(suma,0,sizeof(suma));
        memset(sumb,0,sizeof(sumb));
        memset(sumc,0,sizeof(sumc));
        for(int i = 1;i <= n;++i)
        {
            scanf("%d",&a[i]);
        }
        for(int i = 1;i <= n;++i)
        {
            scanf("%d",&b[i]);
        }
        init();
        LL ans = 0;
        for(int i = 0;i <= n;++i)
        {
            if(i % 2 == 0){
                ans = max(ans,sumc[i] + suma[i + 1] + i * sum[i + 1]);
            }
            else{
                ans = max(ans,sumc[i] + sumb[i + 1] + (i - 1) * sum[i + 1]);
            }
        }
        printf("%lld\n",ans);
    }
    return 0;
}
/*
6
12 8 12 17 20 5
17 4 8 8 8 4
*/