Question

CODE IN C++

Given:

typedef char ItemType;

// a struct type named NodeType that includes a ItemType and pointer

// (to a NodeType) field

struct NodeType {

   ItemType value;

   NodeType * next;

};

bool Delete (NodeType * & firstPtr, ItemType value)

{

   NodeType * prev, * cur;

cur = Search (firstPtr, value, prev);

if (cur==NULL)

return false;

else {

// remove cur node from the linked list

if (prev!=NULL)

{ //not the first one

prev->next = cur->next; //bypass the cur node

}

else //cur is the first node

firstPtr = cur->next; //update the head pointer

delete cur; //deallocate the node itself

return true;

}

}

1. Write a function to search for a value in the linked list, returning both the matching node, and the node before it, i.e. Search function. Note that this function can be used by the following functions:

/* Search for given value in the listed list pointed to by firstNodePtr,

* return the matching node's address, and

* set its previous node's address in prevNode parameter

@param firstNodePtr

@param value

@postcondition: if the value is found in the linked list,

   the node's address will be returned, and

   prevNode will point to the node before; if not found, return NULL, prevNode is NUL L

@return value: same as Search...

*/

NodeType * Search (NodeType * firstNodePtr, ItemType value, NodeType * & prevNode)

{

//Todo by you

}

2. Write a function insert a new node before a node (of a giving value). Write a function that insert a number before an existing node in the linked list storing a certan value, e.g.,

If the linked list contains 1 ->10 -> 30,

and we want to insert a number 20 before node 30, we can call the above

function passing 20, 30 as parameters (in addition to the head), and

after the insertion, the list looks like:

1 -> 10 -> 20 -> 30.

Answer 1

Though, I have documented the code still if you have any doubt feel free to comment. I'll try my best to resolve them as soon as possible.

PS: This program can be done using classes in that case we don't have to pass firstPtr n every function. Also, we can use Search() in insertBefore() and i leave this up to you for practice still if you need any help do let me know.

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Code:

#include <iostream>
using namespace std;
typedef int ItemType;

// a struct type named NodeType that includes a ItemType and pointer
// (to a NodeType) field
struct NodeType {
ItemType value;
NodeType * next;
};

void insertBefore(NodeType* &firstPtr, ItemType value, ItemType target)
       {
       NodeType *t=new NodeType;
       t->value=value;
       t->next=NULL;
       NodeType *p=firstPtr;
           //at the beginning
           if(firstPtr==NULL)
           {
               t->next=NULL;
               firstPtr=t;
               return;
           }
           //if insertbefore first node
           if(firstPtr->value==target)
           {
               t->next=firstPtr;
               firstPtr=t;
               return;
           }
           NodeType *q=firstPtr;
           p=p->next;
           //searching to get the target node
           while(p!=NULL)
           {
               if(p->value==target)
               {
               t->next=q->next;
               q->next=t;
               return;
               }
               q=p;
               p=p->next;
           }
           //if not found
           if(p==NULL)
           {
           cout<<"\nTarget is not found in the list. Hence, inserting at the end.";
           t->next=NULL;
           q->next=t;
           }
           return;
       }
NodeType* Search(NodeType * firstNodePtr, ItemType value, NodeType * & prevNode)
       {
NodeType *p=firstNodePtr;
prevNode=NULL;
if(p->value==value)
{
return p;
}
p=p->next;
prevNode=firstNodePtr;
           while(p!=NULL)
           {
               if(p->value==value)
               {
                   return p;
               }
               prevNode=p;
               p=p->next;
           }
           //not found
           prevNode=NULL;  
           return NULL;
}
  
bool Delete (NodeType * & firstPtr, ItemType value)
{
NodeType * prev, * cur;
cur = Search (firstPtr, value, prev);
if (cur==NULL)
return false;
else{
// remove cur node from the linked list
if (prev!=NULL)
{ //not the first one
prev->next = cur->next; //bypass the cur node
}
else //cur is the first node
firstPtr = cur->next; //update the head pointer
delete cur; //deallocate the node itself
return true;
  
}
}
  
void disp(NodeType * firstPtr)
{
NodeType *p=firstPtr;
if(p==NULL)
{
cout<<"Nothing to display!";
return;
}
cout<<"\n"<<p->value;
p=p->next;
while(p!=NULL)
{
cout<<" -> "<<p->value;
p=p->next;
}
return;
}
  
int main()
{
NodeType* firstPtr=NULL;
disp(firstPtr);
insertBefore(firstPtr,30,0);
disp(firstPtr);
insertBefore(firstPtr,10,30);
disp(firstPtr);
insertBefore(firstPtr,1,10);
disp(firstPtr);
insertBefore(firstPtr,20,30);
disp(firstPtr);
insertBefore(firstPtr,150,45);
disp(firstPtr);
if(Delete(firstPtr,1))
{
cout<<"\nDeleted 1 Sucessfully!";
disp(firstPtr);
}else
cout<<"\nNot Found!";
if(Delete(firstPtr,45))
{
cout<<"\nDeleted 45 Sucessfully!";
disp(firstPtr);
}else
cout<<"\nNot Found!";
return 0;
}
==============

Syntax:

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Output: