#include<iostream>
#include<string>
using namespace std;
int main(){
    string s1,s2,s3,s4;
    cin>>s1>>s2>>s3>>s4;
    string week[7]={"MON","TUE","WED","THU","FRI","SAT","SUN"};
    int flag=0;   //判断是否已找到星期的字符
    for(int i=0;i<s1.size()&&i<s2.size();i++){
        if(s1[i]!=s2[i])
            continue;
        else {
            if(flag==0&&s1[i]>='A'&&s1[i]<='G'){   //判断星期
                       cout<<week[s1[i]-'A']<<" ";
                       flag=1;
                 }
            else if(flag==1&&(s1[i]>='0'&&s1[i]<='9'||s1[i]>='A'&&s1[i]<='N')){  //判断小时
                if(s1[i]>='0'&&s1[i]<='9')
                     cout<<"0"<<s1[i]<<":";
                else
                     cout<<s1[i]-'A'+10<<":";
                break;                
            }
        }
    }
    for(int j=0;j<s3.size()&&j<s4.size();j++)  
        if(s3[j]==s4[j]&&isalpha(s3[j])){     //判断分钟
            printf("%02d",j);
            break;
        }
    return 0;
}

4. 收获

代码中还用到了isalpha函数，判断是否是字母。此外，isalnum函数判断是否是数字或字母；isupper判断是否是大写字母；islower判断是否是小写字母