题解 | 牛牛的考试，这题逻辑太魔鬼了，真的按照题目说的逻辑来写的，都能通过

#include <iostream>
using namespace std;

int main(){
    int T;
    cin>>T;
    for (int i=0; i<T; i++) {
        string a,b,c,d;
        cin>>a;
        cin>>b;
        cin>>c;
        cin>>d;
        int alen=a.length();
        int blen=b.length();
        int clen=c.length();
        int dlen=d.length();
        if (alen>blen&&alen>clen&&alen>dlen
        &&!(blen<alen&&blen<clen&&blen<dlen)
        &&!(clen<alen&&clen<blen&&clen<dlen)
        &&!(dlen<alen&&dlen<clen&&dlen<blen)
        ||alen<blen&&alen<clen&&alen<dlen
        &&!(blen>alen&&blen>clen&&blen>dlen)
        &&!(clen>alen&&clen>blen&&clen>dlen)
        &&!(dlen>alen&&dlen>clen&&dlen>blen)) {
            cout<<'A'<<endl;
        }
        else if (blen>alen&&blen>clen&&blen>dlen
        &&!(alen<blen&&alen<clen&&alen<dlen)
        &&!(clen<alen&&clen<blen&&clen<dlen)
        &&!(dlen<alen&&dlen<clen&&dlen<blen)
        ||blen<alen&&blen<clen&&blen<dlen
        &&!(alen>blen&&alen>clen&&alen>dlen)
        &&!(clen>alen&&clen>blen&&clen>dlen)
        &&!(dlen>alen&&dlen>clen&&dlen>blen)) {
            cout<<'B'<<endl;
        }
        else if (clen>blen&&clen>alen&&clen>dlen
        &&!(alen<blen&&alen<clen&&alen<dlen)
        &&!(blen<alen&&blen<clen&&blen<dlen)
        &&!(dlen<alen&&dlen<clen&&dlen<blen)
        ||clen<alen&&clen<blen&&clen<dlen
        &&!(alen>blen&&alen>clen&&alen>dlen)
        &&!(blen>alen&&blen>clen&&blen>dlen)
        &&!(dlen>alen&&dlen>clen&&dlen>blen)) {
            cout<<'C'<<endl;
        }
        else if (dlen>blen&&dlen>clen&&dlen>alen
        &&!(alen<blen&&alen<clen&&alen<dlen)
        &&!(blen<alen&&blen<clen&&blen<dlen)
        &&!(clen<alen&&clen<blen&&clen<dlen)
        ||dlen<alen&&dlen<clen&&dlen<blen
        &&!(alen>blen&&alen>clen&&alen>dlen)
        &&!(blen>alen&&blen>clen&&blen>dlen)
        &&!(clen>alen&&clen>blen&&clen>dlen)) {
            cout<<'D'<<endl;
        }
        else {
            cout<<'C'<<endl;
        }
    }
}