Searching a Linked List.

[mcap61]

Hey guys,
I have to write a program to check the ranking of the top 1000 boy and girl baby names using linked lists and pointers.

The POINT of the PROGRAM is if you enter a name it will tell you what the name ranks among the list if it is ranked at all.

Result cout should look like this.
Jacob is ranked #1 in popularity among boys.
Jacob is not ranked in the top 1000 girl names.

My problem is in my void check_name() function... the function that checks if the name is in the list and then displays it as well. When the program runs for some reason it only works for the first set of names (the #1 boy and girl) but in an infinite loop.

I have based most of my work off a tutorial from this website
http://richardbowles.tripod.com/cpp/...t/linklist.htm

And here is the link to the list of names. You probably have to save it to a file named babynames2004.txt for the program to work.

http://www.cs.nccu.edu/~gmilledge/co...ynames2004.txt

Sorry if this is confusing Ive been working on this program for way too long.

#include <iostream>
#include <cstdlib>
#include <fstream>

using namespace std;

struct name
       { int rank;
         string boy_name;
         string girl_name;
         name *nxt;
         };
         
name *start_ptr = NULL;
name *current;

void add_names();
void check_name();

string enter_name;

int main()
{
    start_ptr = new name;
    cout << "Please enter a first name to see its ranking" << endl;
    cout << "among the top 1000 baby names." << endl;
    cin >> enter_name;
    cout << endl;
    add_names();
    
    system("PAUSE");
    return 0;
}

    

void add_names()
{   //name *temp, *temp2;
    //temp = new name;
    name * prior = new name;// * temp;
    int ranking;
    int i=0;
    string male_name, female_name;
    ifstream in_stream("babynames2004.txt");
    
    //in_stream.open; //opens and loads names & ranks from file
    if (in_stream.fail())
   {
    cout << "File failed to open." << endl;
    cout << "Program will now close." << endl;
    system("PAUSE");
    exit(0);
   }
    
    in_stream >> ranking>> male_name >> female_name;
	
    
    prior = start_ptr;
    prior->rank = ranking;

    prior->boy_name = male_name;
    prior->girl_name = female_name;
    prior->nxt = NULL;
    
    name *temp;
	while(in_stream >> ranking >> male_name >> female_name)
    {
    
    temp = new name;
    prior->nxt = temp;
    
    temp->rank = ranking;
    temp->boy_name = male_name;
    temp->girl_name = female_name;
    temp->nxt = NULL;
    prior = temp;
    
    }
    temp->nxt = NULL;
}

void check_name()
{   name *strt;
    strt = start_ptr;
    cout << endl;
          
          for (name * strt = start_ptr;strt->nxt !=NULL;strt=strt->nxt)
          {      
            if (enter_name == strt->boy_name && enter_name != strt->girl_name)
            {
                cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
               }
            else (enter_name != strt->boy_name && enter_name != strt->girl_name) 
            {
                 cout << enter_name << " is not ranked among the";
                 cout << " top 1000 boy names." << endl;
                 }
            if (enter_name == strt->girl_name && enter_name != strt->boy_name)
            {
                cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
               }
            else (enter_name != strt->girl_name && enter_name != strt->boy_name)
            {
                cout << enter_name << " is not ranked among the";
                cout << " top 1000 girl names." << endl << endl;
                }
          }
}

[programmersbook]

Hi!

Sorry the http://www.cs.nccu.edu/~gmilledge/co...ynames2004.txt doesnt work.

I think you should use std::list, and no pointers if it's not neccessary! It will make your wile easier ;)

[jonsca]

It's here:
(I helped him on the other post -- mcap, I think you got the abbreviated URL when you cut and pasted)

I think you should use std::list, and no pointers if it's not neccessary!

We can probably do some "duck typing" (go against the C++ grain for a second) on it and find it's an assignment

[mcap61]

sorry here is the link http://www.cs.nccu.edu/~gmilledge/comp1520/comp1520Spring2007/Homework/babynames2004.txt

[mcap61]

oh yeah and one more thing...
The assignment was we are supposed to use pointers and linked lists. But at this point I just want this program to work so yea I'll give std::list a try.

[nezachem]

My problem is in my void check_name() function... the function that checks if the name is in the list and then displays it as well. When the program runs for some reason it only works for the first set of names (the #1 boy and girl) but in an infinite loop.

void check_name()
{   name *strt;
    strt = start_ptr;
    cout << endl;
          
          for (name * strt = start_ptr;strt->nxt !=NULL;strt=strt->nxt)
          {      
                if (enter_name == strt->boy_name && enter_name != strt->girl_name) {}
                // etc
          }
}

In this code, the next search starts from the point where the previous search ended. You need to start each search from the very beginning of the list.

This mistake stems from the wrong design decision: the function that checks if the name is in the list and then displays it as well is a bad function. Split the functionality into "find the record" and "display the (found) record".

[programmersbook]

i would do it like this: http://clipboard.it/v/z2b/ no pointers, better to understand.

[mcap61]

thanks for that programmersbook,
i understand that way better than what i have now, but I still have to use a linked list with pointers.

how would you change the 'for' expression so that it starts at the beginning of the list everytime? i thought i had it with strt=strt->next... guess not.

[programmersbook]

i see, well when i will do it like this:

void check_name()
{   name *strt;
    strt = start_ptr;
    cout << endl;
          
          for (name * strt = start_ptr;strt->nxt !=NULL;strt=strt->nxt)
          {      
          
            if (enter_name == strt->boy_name )
            {
                cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
                break;
            }
            else if (enter_name == strt->girl_name) 
            {
                 cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
                 break;
                              
            }
          }
    cout << enter_name << " is not ranked among the";
      cout << " top 1000 names." << endl;
}

call check_name() after add_names();

Full code:

#include <iostream>
#include <cstdlib>
#include <fstream>

using namespace std;

struct name
       { int rank;
         string boy_name;
         string girl_name;
         name *nxt;
         };
         
name *start_ptr = NULL;
name *current;

void add_names();
void check_name();

string enter_name;

int main()
{
    start_ptr = new name;
    cout << "Please enter a first name to see its ranking" << endl;
    cout << "among the top 1000 baby names." << endl;
    cin >> enter_name;
    cout << endl;
    add_names();
    check_name();
    
    system("PAUSE");
    return 0;
}

    

void add_names()
{   //name *temp, *temp2;
    //temp = new name;
    name * prior = new name;// * temp;
    int ranking;
    //int i=0;
    string male_name, female_name;
    ifstream in_stream("babynames2004.txt");
    
    //in_stream.open; //opens and loads names & ranks from file
    if (in_stream.fail())
   {
    cout << "File failed to open." << endl;
    cout << "Program will now close." << endl;
    system("PAUSE");
    exit(0);
   }
    
    in_stream >> ranking>> male_name >> female_name;
	
    
    prior = start_ptr;
    prior->rank = ranking;

    prior->boy_name = male_name;
    prior->girl_name = female_name;
    prior->nxt = NULL;
    
    name *temp;
	while(in_stream >> ranking >> male_name >> female_name)
    {
    
    temp = new name;
    prior->nxt = temp;
    
    temp->rank = ranking;
    temp->boy_name = male_name;
    temp->girl_name = female_name;
    temp->nxt = NULL;
    prior = temp;
    
    }
    temp->nxt = NULL;
}

void check_name()
{   name *strt;
    strt = start_ptr;
    cout << endl;
          
          for (name * strt = start_ptr;strt->nxt !=NULL;strt=strt->nxt)
          {      
          
            if (enter_name == strt->boy_name )
            {
                cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
                break;
            }
            else if (enter_name == strt->girl_name) 
            {
                 cout << enter_name << " is ranked #" << strt->rank;
                cout << " in popularity among boys.\n" << endl;
                 break;
                              
            }
          }
    cout << enter_name << " is not ranked among the";
      cout << " top 1000 names." << endl;
}