Linked lists in C with explanation for learners

Contents

• Introduction
• Functions
• Main function
• Running the program directly
• Running the program using make
• Explaination of Makefile

Introduction

In this implementation, we define a struct Node that contains an integer data and a pointer to the next Node in the list.

Functions

We then define several functions to manipulate the linked list, including:

• createNode to create a new node
• insertAtBeginning to insert a new node at the beginning of the list
• insertAtEnd to insert a new node at the end of the list
• insertAfter to insert a new node after a given node
• deleteNode to delete a node with a given key
• printList to print the entire linked list

Main function

In the main function of the program, we create a new linked list by initializing the head of the list to NULL using the statement struct Node* head = NULL;.

Next, we insert some nodes into the linked list using the functions insertAtEnd, insertAtBeginning, and insertAfter. Specifically, we insert the nodes with values 1, 2, 3, and 4 into the list. The resulting linked list after these insertions is 2 -> 1 -> 4 -> 3 -> NULL.

We then print the original linked list using the printList function.

After that, we delete a node with a key value of 3 from the list using the deleteNode function.

Finally, we print the resulting linked list again using the printList function.

So, the main function is essentially a test function that creates, manipulates, and prints the linked list to demonstrate how the various functions for manipulating the list work.

Running the program directly

Here are the steps to compile and run the program:

Open the Terminal app on your Mac.

Navigate to the directory where the program source code file is saved using the cd command.

cd ~/directory-name

Compile the program using the following command:

gcc -o linked_list main.c

This will create an executable file named linked_list.

Run the program using the following command:

./linked-list

This will execute the program and you should see the output in the Terminal window.

Running the program using make

To run the program using make, simply run the following command:

make run

To build the program using make, simply run the following command:

make build

You will get an executable file named linked_list. You can then run it.

To clean up the executable file and other files created by make, simply run the following command:

make clean

Explaination of Makefile

Here's a line-by-line explanation:

CC = gcc
CFLAGS = -Wall -g

These lines set the compiler (CC) to gcc and specify some flags (CFLAGS) to use when compiling. Specifically, -Wall tells the compiler to enable all warning messages, and -g tells the compiler to include debugging information in the executable.

clean:
    @echo "Cleaning up..."
    @rm -f linked_list

This is a rule that defines a clean target. When make clean is run, it will execute the commands in this rule. In this case, the rule simply prints a message and removes the linked_list executable.

build: clean
    @echo "Building linked_list..."
    @$(CC) $(CFLAGS) -o linked_list main.c

This is a rule that defines a build target. When make build is run, it will execute the commands in this rule. In this case, the rule first runs the clean target (to remove any existing linked_list executable), then prints a message and compiles main.c into an executable called linked_list.

run: build
    @echo "********************************"
    @echo "Running linked_list..."
    @echo "********************************"
    @echo "Output:"
    @./linked_list

This is a rule that defines a run target. When make run is run, it will execute the commands in this rule. In this case, the rule first runs the build target (to ensure that linked_list is up-to-date), then prints a message and runs the linked_list executable. The output of the executable is printed to the console.

The @ symbols at the beginning of each command tell make to not print the command to the console before executing it. This makes the output of make cleaner and easier to read.