代码如下：

#include<bits/stdc++.h>
using namespace std;
int main(){
    string s1, s2, s3, s4;
    string day[7] = {"MON ", "TUE ", "WED ", "THU ", "FRI ", "SAT ", "SUN "};
    cin>>s1>>s2>>s3>>s4;
    int Min = min(s1.size(), s2.size());
    int i = 0;
    for(; i < Min; i++){
        if(s1[i] == s2[i] && s1[i] >= 'A' && s1[i] <= 'G'){
            cout<<day[s1[i] - 'A'];
            break;
        }
    }
    for(++i; i < Min; i++){
        if(s1[i] == s2[i] && isdigit(s1[i])){
            cout<<"0"<<s1[i]-'0';
            break;
        }
        if(s1[i] == s2[i] && s1[i] >= 'A' && s1[i] <= 'N'){
            cout<<10 + s1[i] -'A';
            break;
        }
    }
    Min = min(s3.size(), s4.size());
    for(int j = 0; j < Min; j++){
        if(s3[j] == s4[j] && isalpha(s3[j])){
            if(j<10)
                cout<<":0"<<j;
            else
                cout<<":"<<j;
            break;
        }
    }
    return 0;
}

笔记：
<ctype.h> 头文件中定义了判断字符的函数
islower(char c) 是否为小写字母
isupper(char c) 是否为大写字母
isdigit(char c) 是否为数字
isalpha(char c) 是否为字母
isalnum(char c) 是否为字母或者数字
toupper(char c) 字母小转大
tolower(char c) 字母大转小