找圆就是矩形对角线（不知道本蒟蒻的垃圾大暴力为什么不对。。）
1 /*#include<bits/stdc++.h> 2 #define N 200005 3 #define LL long long 4 #define inf 0x3f3f3f3f 5 #define ls tr[x][0] 6 #define rs tr[x][1] 7 using namespace std; 8 inline int ra() 9 { 10 int x=0,f=1; char ch=getchar(); 11 while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();} 12 while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();} 13 return x*f; 14 } 15 int a[50]; 16 int main() 17 { 18 int n=ra(),tot=0,ans=0; 19 for (int i=1; i<=n; i++) a[i]=ra(),tot+=a[i]; 20 if (tot%2) { 21 cout<<"0"; 22 return 0; 23 } 24 for (int i=n+1; i<=2*n; i++) a[i]=a[i-n]; 25 for (int k=1; k<n; k++) 26 for (int i=1; i<=n; i++) 27 { 28 int sum=0; 29 for (int j=i; j<=i+k-1; j++) sum+=a[j]; 30 if (2*sum>=tot || (tot-2*sum)%2) break; //break改成continue就AC2333 31 int orz=(tot-2*sum)/2,sum1=0; 32 for (int j=i+k; j<=2*n; j++) 33 { 34 sum1+=a[j]; 35 if (sum1==orz) 36 { 37 int sum2=0; 38 for (int l=j+1; l<=2*n; l++) 39 { 40 sum2+=a[l]; 41 if (sum2==sum) ans++; 42 if (sum2>sum) break; 43 } 44 } 45 if (sum1>orz) break; 46 } 47 // cout<<ans<<"!!";system("pause"); 48 } 49 cout<<ans/4; 50 return 0; 51 }*/ 52 #include<bits/stdc++.h> 53 #define N 200005 54 #define LL long long 55 #define inf 0x3f3f3f3f 56 #define ls tr[x][0] 57 #define rs tr[x][1] 58 using namespace std; 59 inline int ra() 60 { 61 int x=0,f=1; char ch=getchar(); 62 while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();} 63 while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();} 64 return x*f; 65 } 66 int a[50]; 67 int main() 68 { 69 int n=ra(),tot=0,ans=0; 70 for (int i=1; i<=n; i++) a[i]=ra(),tot+=a[i]; 71 if (tot%2) { 72 cout<<"0"; 73 return 0; 74 } 75 for (int i=1; i<=n; i++) 76 { 77 int sum=0; 78 for (int j=i+1; j<=n; j++) 79 { 80 sum+=a[j]; 81 if (sum==tot/2) ans++; 82 } 83 } 84 cout<<(ans*(ans-1)>>1); 85 return 0; 86 }