Question

Please Write the following code in C:

PRELAB - Week of October 14

For this prelab you will implement the following functions:

List * initIntegerList() // Return empty list

int insertAtHead(int k, List*) // Insert k at head

int insertAtTail(int k, List*) // Insert k at tail

int removeHead(List *) // Remove head and return its key

int getListSize(List *) // Return number of elements in list

void printHead(List *) // Print key in head

void moveHeadToTail(List *) // Move key at head to tail

This doesn’t seem so bad – and it isn’t. However, there is a performance requirement that must be satisfied: all of the functions must take only a constant amount of time independent of the length of the list, i.e., they must all have O(1) complexity. Does this make things much more difficult? No, you just need to define a struct (List) that contains a pointer to the head of a linked list; a pointer to the tail of the list; and an integer containing the number of items/keys in the list. (Note that nodes in the linked list will not be List structs.) The information in the List struct is what will allow all operations to be satisfied in O(1) time. Note that the above prototypes impose restrictions on how you handle potential error conditions, e.g., if the user tries to remove the head of an empty list, so you will need to document those situations for the user. For example, the function printHead will need documentation telling the user that nothing is printed if the list is empty. The two insert functions, however, have integer return values that can be used for error codes.

Answer 1

C CODE:

#include <stdio.h>
#include <stdlib.h>

typedef struct Node{
   int data;
   struct Node *next;
} Node;

typedef struct List{
   Node *head, *tail;
   int len;//Number of items in the list
} List;

// Function prototypes
List * initIntegerList(); // Return empty list
int insertAtHead(int k, List*); // Insert k at head
int insertAtTail(int k, List*); // Insert k at tail
int removeHead(List *); // Remove head and return its key
int getListSize(List *); // Return number of elements in list
void printHead(List *); // Print key in head
void moveHeadToTail(List *); // Move key at head to tail

int main(){
   List *l = initIntegerList();//Create an empty list
   insertAtHead(2, l);
   insertAtHead(1, l);
   insertAtTail(4, l);
   insertAtTail(5, l);
   removeHead(l);
   printHead(l);
   printf("Length of list: %d\n", getListSize(l));
   return 0;
}

List* initIntegerList(){
   List *l = (List *)malloc(sizeof(List));
   l->head = NULL;
   l->tail = NULL;
   l->len = 0;
   return l;
}

// This function return 0 if memory allocation fails otherwise 1 on success
int insertAtHead(int k, List* l){
   Node *newNode = (Node*)malloc(sizeof(Node));
   if(newNode == NULL)
      return 0;//Memory allocation failed
   
   newNode->data = k;
   // If list is empty
   if(l->head == NULL){
      newNode->next = NULL;
      l->head = newNode;
      l->tail = newNode;
   }
   else{
      newNode->next = l->head;
      l->head = newNode;
   }
   l->len++;
   return 1;//Indicates value inserted successfully
}

// This function return 0 if memory allocation fails otherwise 1 on success
int insertAtTail(int k, List* l){
   Node *newNode = (Node*)malloc(sizeof(Node));
   if(newNode == NULL)
      return 0;//Memory allocation failed
   
   newNode->data = k;
   newNode->next = NULL;
   // If list is empty
   if(l->tail == NULL){
      l->head = newNode;
   }
   else{
      l->tail->next = newNode;
   }
   l->tail = newNode;
   l->len++;
   return 1;//Indicates value inserted successfully
}

// This function return 0 if list is empty otherwise 1 on success
int removeHead(List *l){
   if(l->len == 0)
      return 0;//Cannot remove. List is empty
   if(l->len == 1){
      free(l->head);
      l->head = NULL;
      l->tail = NULL;
   }
   else{
      Node *temp = l->head->next;
      free(l->head);
      l->head = temp;
   }
   l->len--;
   return 1;//Remove successful
}

int getListSize(List *l){
   return l->len;
}

// This function prints nothing if list is empty
void printHead(List *l){
   // If list is empty
   if(l->len == 0)
      return;
   printf("%d\n", l->head->data);
}

void moveHeadToTail(List *l){
   if(l->len == 0)
      return;
   l->tail->data = l->head->data;
}

OUTPUT:

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