枚举每个球为假，再枚举其是轻是重，带入三个等式或不等式判断，全部符合说明这种情况正确

附代码
#include<iostream>
#include<string>
using namespace std;
int main()
{int n,i,j,x,y,s[15],k,ll,an,l;
string a[4],b[4],c[4],x1="even",
x2="up",x3="down";
char u;
cin>>n;
for (ll=1;ll<=n;ll++)
{
for (i=1;i<=3;i++)
cin>>a[i]>>b[i]>>c[i];
for (i=1;i<=12;i++)
for (l=1;l<=2;l++)
{for (j=1;j<=12;j++)
  s[j]=1;
  s[i]=0;
  an=0;
 for (j=1;j<=3;j++) 
 {x=0;
 for (k=0;k<=a[j].size()-1;k++)
 x=x+s[a[j][k]-'A'+1];
 y=0;
 for (k=0;k<=b[j].size()-1;k++)
 y=y+s[b[j][k]-'A'+1];
 if (c[j]==x1)
 if (x!=y){an=1;break;}
 
 if ((c[j]==x2)and(l==1))
 if (x<=y){an=1;break;}
 
  if ((c[j]==x2)and(l==2))
 if (x>=y){an=1;break;}  
 
  if ((c[j]==x3)and(l==1))
 if (x>=y){an=1;break;}  
 
  if ((c[j]==x3)and(l==2))
 if (x<=y){an=1;break;}
     }  
    u='A'+i-1;
   if (an==0) {cout<<u<<" is the counterfeit coin and it is ";
 if (l==1) cout<<"light.";else cout<<"heavy.";cout<<endl;break;} 
    
    }


}

 }