Linked List: Reprinting the List?

[lllBravolll]

Okay I fixed my code and this is what i got but i cant reprint the list and take out the desired number.
its at the bottom

#include<iostream.h>

struct ListNode
{
int number;
ListNode *link;
};

typedef ListNode* ListNodePtr;

void insertNodeAtFront(ListNodePtr&, int);
void printList(ListNodePtr);
void printReversed(ListNodePtr);
ListNodePtr search(ListNodePtr, int);
void insertAfter(ListNodePtr, int);
void insertAtRear(ListNodePtr, int);
void removeNode(ListNodePtr, ListNodePtr);

void main()
{
ListNodePtr head = new ListNode;
head -> number = 5;
head -> link = NULL;

for(int i = 0; i < 20; i++)
insertNodeAtFront(head, 10*i);

//printList(head);
//printReversed(head);

cout << "What number would you like to find?" << endl;
int target;
cin >> target;
ListNodePtr result = search(head, target);
if(result != NULL)
insertAfter(result, 18);

cout << "What item would you like to remove?" << endl;
cin >> target;
result = search(head, target);
if(result != NULL)
removeNode(head, result);

insertAtRear(head, 99);
printList(head);
int a;
cin >> a;
}

void insertNodeAtFront(ListNodePtr& home, int num)
{
ListNodePtr tempPtr = new ListNode;
tempPtr -> number = num;
tempPtr -> link = home;
home = tempPtr;
}

void printList(ListNodePtr home)
{
for(ListNodePtr here = home; here != NULL; here = here ->link)
{
cout << here -> number << endl;
}
cout << "done" << endl;
}

void printReversed(ListNodePtr here)
{
if(here != NULL)
{
printReversed(here -> link);
cout << here ->number << endl;
}
}

ListNodePtr search(ListNodePtr here, int target)
{
ListNodePtr tempPtr = here;
while((tempPtr -> number != target)&&(tempPtr -> link != NULL))
tempPtr = tempPtr -> link;

if(tempPtr -> number == target)
return tempPtr;
else
return NULL;
}

void insertAfter(ListNodePtr here, int num)
{
ListNodePtr tempPtr = new ListNode;
tempPtr -> number = num;
tempPtr -> link = here -> link;
here -> link = tempPtr;
}

void insertAtRear(ListNodePtr head, int num)
{
ListNodePtr tempPtr = new ListNode;
tempPtr -> number = num;
tempPtr -> link = NULL;
ListNodePtr finder = head;
while(finder -> link != NULL)
finder = finder -> link;
finder -> link = tempPtr;
}


//right here
void removeNode(ListNodePtr head, ListNodePtr here)
{
ListNode *cursor;
for(cursor = head; cursor->link != here; cursor = cursor -> link)
{
cursor->link = head -> link;

}
}

cant get the list to reprint out and take out the desired number.

[looker]

Well let me break your source codes in pieces and go line by line.

#include<iostream.h>

struct ListNode
{
int number;
ListNode *link;
};

typedef ListNode* ListNodePtr;

void insertNodeAtFront(ListNodePtr&, int);
void printList(ListNodePtr);
void printReversed(ListNodePtr);
ListNodePtr search(ListNodePtr, int);
void insertAfter(ListNodePtr, int);
void insertAtRear(ListNodePtr, int);
void removeNode(ListNodePtr, ListNodePtr);

This block of code should be in a header file.....why ?
I do know that it works just the same way as what you did it now, but you will have some big problems in upgradability and scalability. so why ?
What happen when another file .cpp want to call a routine in this prototype ?
or what if your code becomes a Library for the all the Informatics Engineers. So you need to update it to become a solid library right ?

The best way to go is to
- mkdir structure of your files
- Learn to use header file, resource file ....etc
- put the right files in the right folder.

I would suggest you that you better put all the function prototypes, type, #define...etc in a header file.....because it will be easy for readability and your current code will become a very strong library for other to use.

void main()
{
ListNodePtr head = new ListNode;
head -> number = 5;
head -> link = NULL;

First you allocate memory for head, and then you assign the data ( number = 5 ) and the tail of your list = NULL, right ?
At the first view, I also think that it is the right way to go. but it never 100% correct....why ?
I do know that you use new ListNode mean you instructs the system to do it for you. but are you sure 100% that the system will allocates memory for you (head) on the size of your need ? Memory is for everyone to read or write. This is because you assume yourself that everything is fine. but sometime it never.
So i would suggest you to ALWAYS do sanity check on the pointer you allocated before bring do something with it.
so it should look like this

ListNodePtr head = new ListNode;
if (NULL == head)
{
return (something to tell us that there is something wrong);
}
......do your job here....


One more problem with that piece of code. Why you think main should return void ? Are you sure that your main routine works properly and never get bug ?
So if there is a bug in your code, how can you trace out that bug and know what happen ?. You can use dubugger to step over/in each line of code to look for bug right ?....but imagine you have a million lines of code ( like the one of Microsoft ). then how long you spend to check for bug...? i do believe that you will spend a month at least to look for a little bug. WASTING TIME.
So i would suggest that you should return error code to main. it is very helpful to trace out what wrong with code.

for(int i = 0; i < 20; i++)
insertNodeAtFront(head, 10*i);

//printList(head);
//printReversed(head);

cout << "What number would you like to find?" << endl;
int target;
cin >> target;
ListNodePtr result = search(head, target);
if(result != NULL)
insertAfter(result, 18);

cout << "What item would you like to remove?" << endl;
cin >> target;
result = search(head, target);
if(result != NULL)
removeNode(head, result);

insertAtRear(head, 99);
printList(head);
int a;
cin >> a;
}

1.The problem with constant value and string
I think this link below will help you much
http://www.thescripts.com/forum/thread745005.html

2. The problem with calling function
You call insertNodeAtFront(....) and do something after. Why do you believe that insertNodeAtFront work properly and never get bug ? it is because you make sure yourself ( cos you are the author of this code ). But what wrong if there is a bug in your insertNodeAtFront and your code is a library ( the other programmer include your library and use because they are lazy to re-code again ), So do you know what wrong with that bug.....? impossible right ?
So i would love to see you ALWAYS return value for all your functions, and ALWAYS check for return value when calling them in your own function.

3. The problem with your target variable.
Why you are sure that variable target must be integer ?
This is because you assume that the user will enter integer as an input. but do you know the best application is design not for a clever user, but if you can design a very reliable system for DUMMY user, that is the excellent, i think.
So what happen when user ( intentionally or unintentionally ) enter alphabetic data ( a, b ,c ....) So what happen when it reach a line : cin >> target. CRASH
So you better declare target as char or array of char. and then convert it to integer by using atoi(.......), What you need to do next is to check the return value of atoi to make sure that input data is integer or not ? go to http://www.cplusplus.com/reference/c...dlib/atoi.html for reference.

[/quote]

Well let me finish at this point, i will be back tomorrow to go on with other bugs