Thread: pointers to structures

Hey guys, I'm having trouble with this program that I have... a telephone directory system whichs allows user to input name and telephone number and in turn sort the list alphabetically.

Code:

#include<iomanip.h>
#include<string.h>
#include<stdlib.h>
#define MaxName 40
#define Max 100
 
  
   struct Direntry
   {
     char name[MaxName];
     long double tnum;
    
   };

int getDirInfo(Direntry **);
void printSorted(Direntry **, int );
//void findDisp(Direntry **, int );



main()
{  int C, I, x,n;
   Direntry * ade[100]; 
  
 do{
 cout<<"\n\t\t Telephone Directory System \n";
 cout<<"\n Enter directory entries .........................1";
 cout<<"\n Print the directory sorted by name ..............2";
 cout<<"\n Search and display telephone number by name......3";
 cout<<"\n Exit the program.................................0";
 cout<<"\n\n Please enter your choice :"; cin>>x;

 
 switch(x)
   { case 1: n= getDirInfo(ade);
     break;
     case 2: printSorted(ade, n);
     break;
   //case 3: findDisp(ade, n);
   //break;
   }
 }while(x != 0);


}


int getDirInfo(Direntry **pde)
{ 
  int I,num;
  cout<<"\n How many entries do you want to make?: ";
  cin>>num;
   
   for(I=0;I<num;I++)
   {  pde[I]= new Direntry;
   cout<<"\n\n Enter a Name: "; cin.ignore();
   cin.getline((*(pde+I))->name,MaxName);
   cout<<" Enter a phone number: "; cin>>(*(pde+I))->tnum;
  
   cout<<(*(pde+I))->name <<" ";
   cout.setf(ios::fixed);
   cout<<setprecision(0)<<(*(pde+I))->tnum; } 

   return num;
}


void printSorted(Direntry **pde, int n)
{ int C, I, MinIndx; char Min[MaxName];Direntry *Temp[100];
   
 for(C=0;C<(n-1);C++)
   { Min = (*(pde+C))->name;
     MinIndx = C;
     
     for(I=0;I<n;I++)
       {if(strcmp(Min,(*(pde+I))->name)<0)
         { Min=(*(pde +I))->name;
	 MinIndx = I;
	 }
       }
     
     if(strcmp((*(pde+C))->name,Min)<0) //this area is the problem.  How do I put the temporary minimum in Temp? being that I'm using pointer to pointer to structure?  Should I even do it this way? 
       { Temp[C] = (*(pde+C));
         (*(pde+C))= (*(pde+MinIndx));
	 (*(pde+MinIndx))=Temp[C];
	}
    
     cout<<(*(pde+C))->name<<endl;
     cout<<(*(pde+C))->tnum<<endl;     
        
   }
   
}

One other thing... The user inputs the telephone number in consecutive digits like 7321112345. Since it is being stored in a structure, how do i output it like (732)111-2345? It's bugging me!! please help! Any hits are aprreciated. Thanks

Since you wont be performing math on the telephone number, you would probably do better to store it as a string.

Then you could write a function that formats telephone numbers:

Code:

bool format_telephone_number(char* tele_in, char* tele_out)
{
    if ( !tele_in || !tele_out ) return false;
    
    int len = strlen(tele_in);

    if ( len == 7 )
    {
         // format xxx-xxxx
         for ( int i = 0; i < 3; i++ )
             tele_out[i] = tele_in[i];

         // output dash
         tele_out[3]  = '-';

         for ( int j = 3, int k = 4; j < 7; j++, k++)
             tele_out[k] = tele_in[j];
    }
    else if ( len == 10 )
    {
         // format (xxx)xxx-xxxx
         // Add your code here, should be 
         // similar to above
    }
    else
    {
         // your hands are tied: just output the same string
         strcpy(tele_out,tele_in);
    }

     return true;
}

//Then, call like this;

int main()
{
    char output[MaxSize];
    char input[MaxSize];

    // read into input the telephone number

    if (!format_telephone_number(input,output))
    {
        // handle error
    }

    cout<<"Telephone number is"<<output<<endl;

    // etc.

    return 0;
}

oops. I didn't zero terminate that string! Ahh...thats why I use the STL...

Be sure you add the following:

Code:

        // format xxx-xxxx
         for ( int i = 0; i < 3; i++ )
             tele_out[i] = tele_in[i];

         // output dash
         tele_out[3]  = '-';

         for ( int j = 3, int k = 4; j < 7; j++, k++)
             tele_out[k] = tele_in[j];

         // zero terminate the output!
         tele_out[8] = '\0';

Just out of curiosity would I like to be told what would happen if you didn’t made

Code:

int getDirInfo(Direntry **pde)

pde a pointer to a pointer and why. Because I don't get the importance of this. I get that pde is a pointer to an array of pointers, but does that mean it have to be a pointer to a pointer, and still WHY.

alright here's the code. My problem is in the printSorted function... how do I print the sorted list in alphabetical order?

Code:

#include<iomanip.h>
#include<string.h>
#include<stdlib.h>
#define MaxName 40
#define Max 100
 
  
   struct Direntry
   {
     char name[MaxName];
     long double tnum;
    
   };

int getDirInfo(Direntry **);
void printSorted(Direntry **, int );
//void findDisp(Direntry **, int );



main()
{  int C, I, x,n;
   Direntry * ade[100]; 
  
 do{
 cout<<"\n\t\t Telephone Directory System \n";
 cout<<"\n Enter directory entries .........................1";
 cout<<"\n Print the directory sorted by name ..............2";
 cout<<"\n Search and display telephone number by name......3";
 cout<<"\n Exit the program.................................0";
 cout<<"\n\n Please enter your choice :"; cin>>x;

 
 switch(x)
   { case 1: n= getDirInfo(ade);
     break;
     case 2: printSorted(ade, n);
     break;
   //case 3: findDisp(ade, n);
   //break;
   }
 }while(x != 0);


}


int getDirInfo(Direntry **pde)
{ 
  int I,num;
  cout<<"\n How many entries do you want to make?: ";
  cin>>num;
   
   for(I=0;I<num;I++)
   {  pde[I]= new Direntry;
   cout<<"\n\n Enter a Name: "; cin.ignore();
   cin.getline((*(pde+I))->name,MaxName);
   cout<<" Enter a phone number: "; cin>>(*(pde+I))->tnum;
  
   cout<<(*(pde+I))->name <<" ";
   cout.setf(ios::fixed);
   cout<<setprecision(0)<<(*(pde+I))->tnum; } 

   return num;
}


void printSorted(Direntry **pde, int n)
{ int C, I, MinIndx; char Min[MaxName];
   
 for(C=0;C<(n-1);C++)
   { Min = (*(pde+C))->name;
     MinIndx = C;
     
     for(I=0;I<n;I++)
       {if(strcmp(Min,(*(pde+I))->name)<0)
         { Min=(*(pde +I))->name;
	 MinIndx = I;
	 }
       }
     
     if(strcmp((*(pde+C))->name,Min)<0) 
         { Direntry *Temp = (*(pde+C));
         (*(pde+C))= (*(pde+MinIndx));
	 (*(pde+MinIndx))=Temp;
	}

    
     cout<<(*(pde+C))->name<<endl;  // is this the right way to print the sorted list?? something tells me it's not, but i can't think of any other way.
     cout<<(*(pde+C))->tnum<<endl;     
        
   }
   
}