Thread: What is wrong in this??i am tired!

how would you do it?

with only the functions i've provided?

I agree O(2n) is not desirable. Should I just pop the front until it's empty? (I was being lazy...), sorry for the bad example on the destructor.

This is probably more kosher then:

Code:

#include <iostream>

class linklist{
	
	public:
		
		linklist() : head(0) {};
	       ~linklist();
		
		void push_back(int d);
		void pop_front();
		friend void display(linklist& m_list);
	
	private:
	
		struct node{
			
			node(int d) : data(d), next(0) {};
			
			int data;
			node* next;
		};
		
		node* head;
};

linklist::~linklist(){
	
	while(head != 0){
		
		pop_front();
	}
	
	delete head;
}
	

void linklist::push_back(int d){
	
	if(head != 0){
		
		node *curr = head;
		
                while(curr->next != 0){
			
			curr = curr->next;
		}

		curr->next = new node(d);
	}
	
	else{

		head = new node(d);
	}
}

void linklist::pop_front(){
	
	if(head != 0){
		
		node *curr = head;
		
		if(head->next == 0){    // Only one element in list

			delete curr;
			head = 0;
		}
		
		else{

			head = curr->next;
			delete curr;
		}
	}
}
			
			
			

void display(linklist& m_list){
	
	linklist::node *curr = m_list.head;
	
        while(curr != 0){
		
		std::cout << curr->data << "\n";
		curr = curr->next;
	}
}


/*  MAIN:
*/
int main(){
	
	linklist m_list;
	
	for(int i = 0; i < 10; i++)
		m_list.push_back(i + 1);
	
	display(m_list);
	
	return 0;
}

Now you're talking!
This would do it:

Code:

linklist::~linklist() {	
	while(head != 0)
		pop_front();
}

There's one thing I don't like about the list implementation, the fact that I need to declare display() as a friend function. What I'd rather do is make an iterator class within list that outsiders can use to traverse the list.

So, we can add the iterator class to the public interface of list:

Code:

public:
	
        class iterator{
                
            public:
            
                iterator( node* c = 0 ) : curr( c ) {};
                
                int operator*( ) { return curr->data; };
                bool operator!=( const iterator& i ) { return i.curr != curr; };
                bool operator==( const iterator& i ) { return i.curr == curr; };
                iterator& operator++( ) { curr = curr->next; return *this; };

             private:
                
                node* curr;
        };
        
        const iterator begin() const{ return iterator(head); };

Then instead of needing to hard code friend functions into the header we can write our own functions and use iterators to gain access to the next->

Code:

void iter_display(linklist& m_list){
	
	for(linklist::iterator it = m_list.begin(); it != 0; ++it){
		
		std::cout << *it << "\n";
	}
}