Question

It is about C++linked list code. my assignment is making 1 function, in below circumstance,(some functions are suggested for easier procedure of making function.)

void pop_Stack (struct linked_list* list, int number) //*This is the function to make and below is the explanation that should be written in given code.

This function removes some nodes in stack manner; the tail of the list will be removed, repeatedly. The parameter (variable 'number') means the number of nodes that will be removed. When parameter is bigger than 1, popping a node with n times, you do not remove node at one go. If there is only one node in the list, please make sure it frees (de-allocates) both the node and the list. If the list is not a stack type(list->type_of_list!=1), print the error message “Function pop_Stack: The list type is not a stack” and exit the function. If the 'number' parameter is less than 1 or more than the number of nodes in the stack, respectively print the error message “Function popStack: The number of nodes which will be removed is more than 1” and “Function popStack: The number of nodes which will be removed is more than that in the stack”, then exit the function. The removed nodes should be freed.

Given code is written below,(There is a function to fill in last moment in this code)

linked_list.h: This is the header file of linkLQS.c that declares all the functions and values that are going to be used in linkLQS.c. You do not have to touch this function.

-----------------------------------------------------------------------

(Below code is about linked_list.h)

#include
#include
#include

struct linked_node{
   int value;
   struct linked_node* next;
   struct linked_node* prev;
};

struct linked_list{
   int type_of_list; // normal = 0, stack = 1
   struct linked_node* head;
   struct linked_node* tail;
   int number_of_nodes;
};

-----------------------------------------------------------------------------------------------------------------------------

#include "linked_list.h"
#include "string.h"

int list_exist;

struct linked_list* create_list (int number_of_nodes, int list_type)
{
   int a[number_of_nodes];
   int i, j;
   int bFound;

   if (number_of_nodes < 1)
   {
       printf("Function create_list: the number of nodes is not specified correctly\n");
       return NULL;
   }
   if(list_exist == 1)
   {
       printf("Function create_list: a list already exists\nRestart a Program\n");
       exit(0);  
   }
   if(list_type != 0 && list_type != 1)
   {
       printf("Function create_list: the list type is wrong\n");
       exit(0);  
   }
   struct linked_list * new_list = (struct linked_list*)malloc(sizeof(struct linked_list));
   new_list->head = NULL;
   new_list->tail = NULL;
   new_list->number_of_nodes = 0;
   new_list->type_of_list = list_type;

   //now put nodes into the list with random numbers.
   srand((unsigned int)time(NULL));
   if(list_type == 0)
   {
       for ( i = 0; i < number_of_nodes; ++i )
       {
           while ( 1 )
           {
  
               a[i] = rand() % number_of_nodes + 1;
               bFound = 0;
               for ( j = 0; j < i; ++j )
               {
                   if ( a[j] == a[i] )
                   {
                       bFound = 1;
                       break;
                   }
               }
               if ( !bFound )
                   break;
           }
           struct linked_node* new_node = create_node(a[i]);
           insert_node(new_list, new_node);
       }
   }
   else if(list_type == 1)
   {
       for ( i = 0; i < number_of_nodes; ++i )
       {
           while ( 1 )
           {
  
               a[i] = rand() % number_of_nodes + 1;
               bFound = 0;
               for ( j = 0; j < i; ++j )
               {
                   if ( a[j] == a[i] )
                   {
                       bFound = 1;
                       break;
                   }
               }
               if ( !bFound )
                   break;
           }
           struct linked_node* new_node = create_node(a[i]);
           push_Stack(new_list, new_node);
       }
   }
   list_exist = 1;
   printf("List is created!\n");
   return new_list;
}

struct linked_node* create_node (int node_value)//This functon is the example for reference of the assignment function
{
   struct linked_node* node = (struct linked_node*)malloc(sizeof(struct linked_node));
   node->value = node_value;
   node->next = NULL;
   node->prev = NULL;
   return node;
}

void insert_node(struct linked_list* list, struct linked_node* node)//This functon is the example for reference of the assignment function
{
   node->next = NULL;
   node->prev = NULL;

   if(list->head == NULL)       //if head is NULL, tail is also NULL.
   {
       list->head = node;
       list->tail = node;
       list_exist = 1;
   }
   else if(list->head == list->tail)
   {
       node->next = list->head;
       list->head->prev = node;
       list->head = node;
   }
   else if(list->head != list->tail)
   {
       node->next = list->head;
       list->head->prev = node;
       list->head = node;
   }
   (list->number_of_nodes)++;
}

void pop_Stack(struct linked_list* list, int number)//The function to be written!!
{
~~~~~~~~~~~~~ //your code starts from here
}

Answer 1

void pop_Stack(struct linked_list* list,int number){
    if(list->type_of_list != 1){
        printf("Function pop_Stack: The list type is not stack\n");
        return;
    }
    if(number < 1){
        printf("Function pop_Stack: the number of nodes which will be removed is less than 1\n");
        return ;
    }

    if(number > list->number_of_nodes){
        printf("Function pop_Stack: the number of nodes which will be removed is grater than in the stack\n");
        return ;
    }

    while(number){
        struct linked_node* temp = list->tail;            // save the address of last node in a temprory variable
        list->tail = list->tail->prev;      // move to tail one step back
        if(list->tail != NULL)
            list->tail->next = NULL;                  // make tail's next to point nowhere
        free(temp);                         // free the node
        list->number_of_nodes--;            // decrease the number of nodes
        number--;
    }
    if( list->number_of_nodes == 0 ){
        free(list);
        
    }
    return;
}