【BZOJ-2937】建造酿酒厂 前缀和 + 展环为链 + 乱搞

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
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;
}
#define maxn 10100
int n,need[maxn<<1],dis[maxn<<1];
long long sumn[maxn<<1],sumd[maxn<<1];
int main()
{
    n=read();
    for (int ne,dd,i=1; i<=n; i++) 
        ne=read(),dd=read(),need[i+n]=need[i]=ne,dis[i+n]=dis[i]=dd;
    for (int i=1; i<=n<<1; i++) sumn[i]=sumn[i-1]+need[i];
    for (int i=1; i<=n<<1; i++) sumd[i]=sumd[i-1]+dis[i-1];
    long long ans=0,tmp; int po=1;
    for (int i=2; i<=n; i++) ans+=(long long)need[i]*min(sumd[i],sumd[1+n]-sumd[i]);
    for (;sumd[po+1]<sumd[n+1]-sumd[po+1]; po++);
    tmp=ans;
    for (int i=2; i<=n; i++)
        {
            tmp+=(long long)dis[i-1]*(sumn[n+i-1]-sumn[po]-(sumn[po]-sumn[i-1]));  
            for(;sumd[po+1]-sumd[i]<sumd[n+i]-sumd[po+1];po++)
                tmp+=(long long)need[po+1]*(sumd[po+1]-sumd[i]-(sumd[n+i]-sumd[po+1]));  
            ans=min(ans,tmp);
        }
    printf("%lld\n",ans);
    return 0;
}