Week 9 Lecture Code

// Pantea Aria
// linked list introduction

// What is a linked list? How is it different from an array? static memory 
// collection of same data type - dynamic memory in linked list malloc 

// Draw a linked list of three nodes with values 10, 20, and 30.

// What does the last node of a singly linked list point to? NULL

// make linked lists with 3 nodes, print each node's data
    
#include <stdio.h>
#include <stdlib.h>

struct node {
    int data;
    struct node *next;
};

int main (void) {

    // declare, malloc and initialise for first node
    struct node *first = malloc(sizeof(struct node));
    // always check if it is not returning NULL your turn
    first->data = 10;
    first->next = NULL;
    // declare, malloc and initialise for second node
    struct node *second = malloc(sizeof(struct node));
        // always check if it is not returning NULL your turn
    second->data = 20;
    second->next = NULL;    
    // declare, malloc and initialise for third node
    struct node *third = malloc(sizeof(struct node));
    // always check if it is not returning NULL your turn
    third->data = 30;
    third->next = NULL;
    // link first to second
    // I must update the first node's next
    first->next = second;
    // link second to third
    // I must update the next of second node
    second->next = third;
  
    // print out all values using first node
    printf("%d %d %d\n", first->data, 
        first->next->data, 
        first->next->next->data);
    
    
    // print all next
    printf("%p %p %p\n", first, first->next, first->next->next);
    printf("%p %p %p\n", first, second, third);

    free(first);
    free(second);
    free(third);
    return 0;
}    
    
    
    
    
    
    
    
    

// Pantea Aria
// linked list functions

// Draw a linked list of three nodes with values 10, 20, and 30.

// make linked lists with 3 nodes values 10, 20, and 30
// print each node's data using a function
    
#include <stdio.h>
#include <stdlib.h>

struct node {
    int data;
    struct node *next;
};
void print_list(struct node *head);
int main (void) {

    // declare, malloc and initialise for first node
    struct node *first = malloc(sizeof(struct node));
    if (first == NULL) {
            // print the error
            return 1;
    }
    first->data = 10;  
    // declare, malloc and initialise for second node
    first->next = malloc(sizeof(struct node));
    // test if it is not NULL - your turn
    first->next->data = 20;    
    // declare, malloc and initialise for third node
    first->next->next = malloc(sizeof(struct node));
    // test if it is not NULL - your turn
    first->next->next->data = 30;
    // I must set the last node's next to NULL
    first->next->next->next = NULL;
    
    // print out all values
    printf("%d %d %d\n", first->data, 
        first->next->data, first->next->next->data);
      
    // cal print_list
    print_list(first);

    
    return 0;
} 
void print_list(struct node *head) {
    // make a temporary pointer to travers my linked list
    struct node *current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
} 
    
    
    
    
    
    
    
    

// Pantea Aria

// Linked Lists - Create, travers, insert 

// Build a linked list by inserting values 0 to 9
// at the end (tail) of an initially empty list

// Use a loop to repeatedly add each new node to the tail

// free functions for later

// For now, this program will leak memory

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

struct node {
    int data;
    struct node *next;
};

// TODO 1:
// Write the function prototypes for:
// - create_node
struct node *create_node(int data, struct node *next);
// - print_list
void print_list(struct node *head);
// - insert_at_tail
struct node *insert_at_tail(struct node *head, int data);
// - list_length
int list_length(struct node *head);
// - insert_at_middle
struct node *insert_at_middle(struct node *head, int data);



int main(void) {

    // TODO 2:
    // Declare a pointer called head and initialise it to NULL
    // This will represent an empty linked list
    struct node *head = NULL;

    // TODO 3:
    // Use a loop to insert values 0–9 at the START of the list
    // (Hint: create_node should be used here)
    // After each insertion, print the list
    for (int i = 0; i < 10; i++) {
        struct node *new_node = create_node(i, head);
        head = new_node;
        print_list(head);
    }


    // TODO 4:
    // Create a second list called head2
    // Insert values 0–9 at the END of the list using insert_at_tail
    // After each insertion:
    //   - Print the list length
    //   - Print the list contents


    // TODO 5:
    // Insert the value 99 into the middle of head2
    // Print the new length and the updated list


    // TODO 6:
    // Create a third list (empty)
    // Insert 42 into the middle of this empty list
    // Print the result


    return 0;
}


// TODO 7:
// Implement create_node
// - Allocate memory
// - Check if malloc returned NULL
// - Initialise data and next
// - Return the new node
struct node *create_node(int data, struct node *next) {
    struct node *new = malloc(sizeof(struct node));
    if (new == NULL) {
        return NULL;
    }
    new->data = data;
    new->next = next;

    return new;
}



// TODO 8:
// Implement print_list
// - Traverse from head to NULL
// - Print each data value
void print_list(struct node *head) {
    // make a temporary pointer to travers my linked list
    struct node *current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
} 


// TODO 9:
// Implement insert_at_tail
// - Create a new node
// - If list is empty, return new node as head
// - Otherwise traverse to the last node
// - Attach new node at the end
// - Return head



// TODO 10:
// Implement list_length
// - Traverse the list
// - Count how many nodes exist
// - Return the count



// TODO 11:
// Implement insert_at_middle
// - Create a new node
// - If list is empty, return new node
// - Find the position size/2
// - Move to the node before that position
// - Adjust pointers to insert the new node
// - Return head

// Pantea Aria

// Returning a pointer to a struct
// Dynamic memory allocation using malloc
// dereferencing using -> 
// Freeing memory using free



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

#define MAX_LEN 100

struct student {
    char name[MAX_LEN];
    int id;
};

// Function prototypes
struct student *create_student(char *name, int id);
void print_student(struct student s);

int main(void) {

    // 1. Create a student id =12345 name = "Pantea Aria"
    

    // 2. Print student details
    

    // 3. Free allocated memory
    

    return 0;
}

// Function to create a student and return pointer - ToDo
struct student *create_student(char *name, int id) {
    // allocate memory for the student 
    
    // check if malloc worked correctly
    
    // assign name and id to the new struct 
    
    // return the new student

    
}

// Function to print student details - ToDo
void print_student(struct student s) {
    printf("Name: %s\n", s.name);
    printf("ID: %d\n", s.id);
}

// Pantea Aria
// linked list introduction

// What is a linked list? How is it different from an array? static memory 
// collection of same data type - dybnamic memory in linked list malloc 

// Draw a linked list of three nodes with values 10, 20, and 30.

// What does the last node of a singly linked list point to? NULL

// make linked lists with 3 nodes, print each node's data
    
#include <stdio.h>
#include <stdlib.h>

struct node {
    int data;
    struct node *next;
};

int main (void) {

    // declare, malloc and initialise for first node

    
    // declare, malloc and initialise for second node

    
    // declare, malloc and initialise for third node

    
    // link first to second

    
    // link second to third

    
    // print out all values
    
    
    // print all next

    
    return 0;
}    
    
    
    
    
    
    
    
    

// Pantea Aria
// linked list functions

// Draw a linked list of three nodes with values 10, 20, and 30.

// make linked lists with 3 nodes values 10, 20, and 30
// print each node's data using a function
    
#include <stdio.h>
#include <stdlib.h>

struct node {
    int data;
    struct node *next;
};

int main (void) {

    // declare, malloc and initialise for first node

    
    // declare, malloc and initialise for second node

    
    // declare, malloc and initialise for third node

    
    // link first to second

    
    // link second to third

    
    // print out all values
    
    
    // cal print_list

    
    return 0;
}    
    
    
    
    
    
    
    
    

// Pantea Aria

// Linked Lists - Create, travers, insert 

// Build a linked list by inserting values 0 to 9
// at the end (tail) of an initially empty list

// Use a loop to repeatedly add each new node to the tail

// free functions for later

// For now, this program will leak memory

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

struct node {
    int data;
    struct node *next;
};

// TODO 1:
// Write the function prototypes for:
// - create_node
// - print_list
// - insert_at_tail
// - list_length
// - insert_at_middle



int main(void) {

    // TODO 2:
    // Declare a pointer called head and initialise it to NULL
    // This will represent an empty linked list


    // TODO 3:
    // Use a loop to insert values 0–9 at the START of the list
    // (Hint: create_node should be used here)
    // After each insertion, print the list


    // TODO 4:
    // Create a second list called head2
    // Insert values 0–9 at the END of the list using insert_at_tail
    // After each insertion:
    //   - Print the list length
    //   - Print the list contents


    // TODO 5:
    // Insert the value 99 into the middle of head2
    // Print the new length and the updated list


    // TODO 6:
    // Create a third list (empty)
    // Insert 42 into the middle of this empty list
    // Print the result


    return 0;
}


// TODO 7:
// Implement create_node
// - Allocate memory
// - Check if malloc returned NULL
// - Initialise data and next
// - Return the new node



// TODO 8:
// Implement print_list
// - Traverse from head to NULL
// - Print each data value



// TODO 9:
// Implement insert_at_tail
// - Create a new node
// - If list is empty, return new node as head
// - Otherwise traverse to the last node
// - Attach new node at the end
// - Return head



// TODO 10:
// Implement list_length
// - Traverse the list
// - Count how many nodes exist
// - Return the count



// TODO 11:
// Implement insert_at_middle
// - Create a new node
// - If list is empty, return new node
// - Find the position size/2
// - Move to the node before that position
// - Adjust pointers to insert the new node
// - Return head