CodeForces 375A Divisible By Seven

Divide this string of numbers into three parts: "1689", "0", and "others.

In the third part, * 10000 is used to obtain the remainder of 7, and then the remainder of the third part is used in the case of "1689". Finally, all 0 values are output.

The first time I did this kind of question, I had no idea at all. It was all taken by senior students .....

#include 
 
  #include 
  
   #include 
   
    #include #include 
    
     #include 
     
      #include 
      
       #define LL long longusing namespace std;char s[1001000];char w[1001000];bool mark[11];int main(){ memset(mark,false,sizeof(mark)); LL top = 0,sum = 0,i,Zero = 0; cin>>s; int len = strlen(s); for(i = 0;i < len; ++i) { if((s[i] == '1' || s[i] == '6' || s[i] == '8' || s[i] == '9') && mark[s[i]-'0'] == false) { mark[s[i]-'0'] = true; } else if(s[i] == '0') { Zero ++; } else { w[top++] = s[i]; } } for(i = 0;i < top; ++i) { sum *= 10; sum += (w[i]-'0'); sum %= 7; } sum *= 10000; sum %= 7; for(i = 0;i < top; ++i) { printf("%c",w[i]); } switch(sum) { case 0:printf("1869");break;// case 6:printf("1968");break; case 5:printf("1689");break;// case 4:printf("6198");break; case 3:printf("8691");break; case 2:printf("9861");break;// case 1:printf("8196");break;// } while(Zero--) { printf("0"); } cout<