Question

Below is a definition of the class of the circular link list.

class CircChain;

class ChainNode {

friend class CircChain;

private:

int data;

ChainNode *link ;

};

class CircChain{

public:

...

private:

ChainNode *last; // The last node points.

}

=>

Create a member function to delete the last node. Returns false if empty list; otherwise, delete last node and return true.

'Bool CircChain::DeleteLastNode()'

Answer 1

Hello!

Here the last node is always the new node created.

Before we assign last to node we have to make sure the previous node get the link for newly created node

And if you understand that then it will easy , so please take time and understand the concepts as i have used comments also.

In delete:

I will travel from first node and when i encounter the first node i will stop and changes the links of the node

So everything i have explained in comments please take some time and get clear idea and let me know if you have any doubts regarting the concept and the doubt regarding to any line of the code.

CODE:

#include <iostream>
using namespace std;
class CircChain;

class ChainNode {

friend class CircChain;

private:

int data;

ChainNode *link ;

};

class CircChain{

public:
CircChain(){
    last = NULL;
}
// method for inserting data 
void insert(int data){
    // creating a pointer object of ChainNode
    ChainNode *node = new ChainNode;
    // data is given to node created
    node->data = data;
    node->link = NULL;
    // if no node is present
    if(last == NULL){
        // last points the created node
        last = node;
        // link of node point the last node
        node->link = last;
    }
    // if atleast one node exists
    else{
        ChainNode *temp = new ChainNode;
        // temp stores the node linked for last node
        temp = last->link;
        // last node link gets changed to new node 
        last->link = node;
        // node link points to the first node
        node->link = temp;
        // the last node becomes the node created
        last = node;
    }

}
void show(){
    ChainNode *node = new ChainNode;
    // node will have the first node 
    node = last->link;
    // checks the node having link to last node
    while(node != last){
        // prints the data in node
        cout << node->data << endl;
        // node gets changed to linked node
        node = node->link;
    }
    cout << node->data << endl;
}
bool DeleteLastNode(){
    // returns false if last points to NULL
    if(last == NULL){
        return false;
    }
    // else deletes the last node
    else{
        ChainNode *node = new ChainNode;
        // node points to the first node of list
        node = last->link;
        // checks the node having link to last node
        while(node->link != last){
            // node gets changed to linked node
            node = node->link;
        }
        //node link gets updated with last linked node
        node->link = last->link;
        // finally the last points to last node 
        last = node;
        // and returns true
        return true;
    }
}
private:

ChainNode *last; // The last node points.

};
int main() {
    // creating a circular linked list
    CircChain c;
    // before inserting data
    cout << "Before inserting data \n***Deleting node**** \n";
    cout << "Last node deleted: " << c.DeleteLastNode() << endl;
    cout << "Inserting data\n";
    // inserting data into list
    c.insert(15);
    c.insert(24);
    c.insert(6);
    cout << "Elements before deletion:\n";
    // displaying data after insertion
    c.show();
    // deleting the last node 
    cout << "***Deleting node**** \n";
    cout << "Last node deleted: " << c.DeleteLastNode() << endl;
    cout << "Elements after deletion:\n";
    c.show();
        return 0;
}

OUTPUT:

Hope this helps and clear.

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Thank you!