【枚举】bzoj1800 [Ahoi2009]fly 飞行棋

 1 #include<cstdio>
 2 #include<algorithm>
 3 using namespace std;
 4 int n,a[101],sum[101],half,ans;
 5 int query(const int &A,const int &B)
 6 {
 7     int x=max(A,B),y=min(A,B),res=sum[x-1]-sum[y-1];
 8     if(res>half) return sum[n]-res;
 9     else return res;
10 }
11 int main()
12 {
13     scanf("%d",&n);
14     for(int i=1;i<=n;i++)
15       {
16           scanf("%d",&a[i]);
17           sum[i]=sum[i-1]+a[i];
18       }
19     half=sum[n]>>1;
20     for(int i=1;i<=n;i++)
21       for(int j=i+1;j<=n;j++)
22         for(int k=j+1;k<=n;k++)
23           for(int l=k+1;l<=n;l++)
24             if(query(i,j)==query(k,l)&&query(j,k)==query(l,i))
25               ans++;
26     printf("%d\n",ans);
27     return 0;
28 }