Question

1. Write the implementation of a non-member function Node* deleteSecond(Node* head_ptr), where Node is a class defined on page 257. The function takes as input a pointer to the head of a linked list consisting of numbers. The function should remove the second item in the list. If the list had only one item, the function should delete that item. If the list was empty, then let the list remain empty. In all cases return the new head of the list

Node class:

#ifndef MAIN_SAVITCH_NODE1_H
#define MAIN_SAVITCH_NODE1_H
#include <cstdlib> // Provides size_t and NULL

namespace main_savitch_5 {

class node {
public:

// TYPEDEF
typedef double value_type;
// CONSTRUCTOR
node(const value_type& init_data=value_type( ), node* init_link=NULL)

{ data_field = init_data; link_field = init_link; }
// MODIFICATION MEMBER FUNCTIONS
node* link( ) { return link_field; }
void set_data(const value_type& new_data) { data_field = new_data; } void set_link(node* new_link) { link_field = new_link; }

// CONST MEMBER FUNCTIONS
value_type data( ) const { return data_field; } const node* link( ) const { return link_field; }

private:
value_type data_field; node *link_field;

};

// FUNCTIONS for the linked-list toolkit
std::size_t list_length(const node* head_ptr);
void list_head_insert(node*& head_ptr, const node::value_type& entry); void list_insert(node* previous_ptr, const node::value_type& entry); node* list_search(node* head_ptr, const node::value_type& target); const node* list_search

(const node* head_ptr, const node::value_type& target);
node* list_locate(node* head_ptr, std::size_t position);
const node* list_locate(const node* head_ptr, std::size_t position); void list_head_remove(node*& head_ptr);
void list_remove(node* previous_ptr);
void list_clear(node*& head_ptr);
void list_copy(const node* source_ptr, node*& head_ptr, node*& tail_ptr);

} #endif

Answer 1

• Node *deleteSecond(Node *head_ptr){
     if(head_ptr == NULL){
         return head_ptr; // return empty list
     }else if(head_ptr->link_field == NULL){ // if one element remove it
         head_ptr = head_ptr->link_field;
         return head_ptr;
     }else{
         // if more than two element remove second element
         head_ptr->link_field = head_ptr->link_field->link_field;
         return head_ptr;
     }
    
  }