1016C - Vasya And The Mushrooms - CodeForces Solution

#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read(){
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-') f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=x*10+ch-'0';
		ch=getchar();
	}
	return x*f;
} 
const int N=3e5+5;
int a[2][N],dis[2][N],dis2[2][N],dis3[2][N];
signed main(){
	int n=read();
	for(int i=0;i<2;++i){
		for(int j=1;j<=n;++j){
			a[i][j]=read(); 
		}
	}
	for(int i=1;i<=n;++i){
		for(int j=0;j<2;++j){
			dis[j][i]=dis[j][i-1]+((i%2)==j)*(a[1-j][i-1]*((i-1)*2-((i-1)%2!=1-j)-1)+a[1-j][i]*(i*2-(i%2!=1-j)-1))+a[j][i]*(2*i-(i%2!=j)-1);  
		}
	}
	int mx=max(dis[0][n],dis[1][n]);
	int k=0;
	for(int i=0;i<2;++i){
		for(int j=n;j>0;--j){
			dis2[i][j]=dis2[i][j+1]+a[i][j]*(j-1);
			dis3[i][j]=dis3[i][j+1]+a[i][j]; 
		}
	}
	for(int i=1;i<n;++i){
		int sum=dis[1-i%2][i-1];
		int sum2=dis2[1-i%2][i]+(i-1)*dis3[1-i%2][i];
		int sum3=(2*n-2+i)*dis3[i%2][i]-dis2[i%2][i];
		mx=max(mx,sum+sum2+sum3);
	}
	printf("%lld\n",mx);
	return 0;
}