DSA Project – To Do List

Program 1

// TO DO List Project Based on Linked List
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Task 
{
    int id;
    char description[100];
    int completed;
    struct Task* next;
} Task;

Task* head = NULL;    // First Node 
int taskCount = 0;

// Function to create a new task
Task* createTask(char desc[]) 
{
    Task* newTask = (Task*)malloc(sizeof(Task));
    newTask->id = ++taskCount;
    strcpy(newTask->description, desc);
    newTask->completed = 0;
    newTask->next = NULL;
    return newTask;
}

// Function to add a task
void addTask() 
{
    char desc[100];
    getchar();  // clear buffer
    printf("Enter task description: ");
    fgets(desc, sizeof(desc), stdin);
    desc[strcspn(desc, "\n")] = '\0';  // remove newline

    Task* newTask = createTask(desc);

    if (head == NULL) 
    {
        head = newTask;
    } else 
    {
        Task* temp = head;
        while (temp->next != NULL)
            temp = temp->next;
        temp->next = newTask;
    }
    printf("Task added successfully.\n");
}

// Function to display all tasks
void displayTasks() 
{
    if (head == NULL) 
    {
        printf("To-Do List is empty.\n");
        return;
    }

    Task* temp = head;
    printf("\nTo-Do List:\n");
    while (temp != NULL) 
    {
        printf("ID: %d | [%s] %s\n", temp->id,temp->completed ? "X" : "*", temp->description);
        temp = temp->next;
    }
}

// Function to mark a task as completed
void markCompleted() 
{
   if(head==NULL) 
    printf("To do list is empty");
else
{
    int id;
    printf("Enter task ID to mark as completed: ");
    scanf("%d", &id);

    Task* temp = head;
    while (temp != NULL) 
    {
        if (temp->id == id) 
        {
            temp->completed = 1;
            printf("Task marked as completed.\n");
            return;
        }
        temp = temp->next;
    }
    printf("Task with ID %d not found.\n", id);
}   
}

// Function to delete a task
void deleteTask() 
{
    int id;
    printf("Enter task ID to delete: ");
    scanf("%d", &id);

    Task *temp = head, *prev = NULL;

    while (temp != NULL && temp->id != id) 
    {
        prev = temp;
        temp = temp->next;
    }

    if (temp == NULL) 
    {
        printf("Task with ID %d not found.\n", id);
        return;
    }

    if (prev == NULL) 
    {
        head = temp->next;
    } else 
    {
        prev->next = temp->next;
    }

    free(temp);
    printf("Task deleted successfully.\n");
}

// Main menu
int main() 
{
    int choice;

    do 
    {
        printf("\n----- To-Do List Menu -----\n");
        printf("1. Add Task\n");
        printf("2. Display Tasks\n");
        printf("3. Mark Task as Completed\n");
        printf("4. Delete Task\n");
        printf("5. Exit\n");
        printf("---------------------------\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) 
        {
            case 1: addTask(); break;
            case 2: displayTasks(); break;
            case 3: markCompleted(); break;
            case 4: deleteTask(); break;
            case 5: printf("Exiting program.\n"); break;
            default: printf("Invalid choice. Try again.\n");
        }

    } while (choice != 5);

    return 0;
}