【bzoj4412】[Usaco2016 Feb]Circular Barn

先看成一条链

for一遍找位置

在for一遍算答案

 #include<algorithm>
 #include<iostream>
 #include<cstring>
 #include<string>
 #include<cstdio>
 #include<cmath>
 using namespace std;
 
 typedef long long LL;
 
 #define N 100010
 
 int n;
 int cnt=;
 
 int a[N<<],s[N<<];
 
 int main()
 {
     freopen("a.in","r",stdin);freopen("a.out","w",stdout);
     scanf("%d",&n);
     for (int i=;i<=n;i++)
         scanf("%d",&a[i]),a[n+i]=a[i];
     for (int i=;i<=n*;i++)
     {
         if (i==cnt+n)
             break;
         s[i]=s[i-]+a[i]-;
         while (s[i]<s[cnt-])
             cnt++;
     }
     LL ans=;
     int l=cnt+n-,r=cnt+n-;
     while (r>=cnt)
     {
         while (!a[l])
             l--;
         ans+=(LL)(r-l)*(r-l);
         a[l]--;
         r--;
     }
     printf("%lld\n",ans);
     return ;
 }