Description:

This C program is a basic To-Do List Manager that lets users create categories and tasks within those categories. Users can add categories, add tasks to categories, delete tasks, display tasks by category, and count the total number of tasks. The data structure used is a singly linked list for both categories and tasks.

Data Structures:

Category: Represents a to-do list category, containing a category_name and a linked list of tasks.

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struct category {
    char category_name[100];
    struct task* tasks;
    struct category* next;
};

Task: Represents an individual task within a category.

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struct task {
    char task_about[100];
    struct task* next;
};

Functions: create_task: Creates a new task node and initializes it with a task description.

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struct task* create_task(const char* task_about);

create_category: Creates a new category node and initializes it with a category name.

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struct category* create_category(const char* category_name);

find_category: Searches for a category by name in the linked list of categories.

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struct category* find_category(struct category* head, const char* category_name);

add_task: Adds a new task to a given category.

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void add_task(struct category* category_name, const char* task_about);

delete_task: Deletes a task from a given category by its task description.

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void delete_task(struct category* category_name, const char* task_about);

count_task: Counts the total number of tasks across all categories.

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int count_task(struct category* head);

display_task_by_category: Displays tasks categorized by their category names.

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void display_task_by_category(struct category* head);

Main Menu:

The program operates through a menu-driven interface with six options:

1. Add Category: Adds a new category to the list.
2. Add Task: Adds a task to a selected category.
3. Delete Task: Deletes a task from a selected category.
4. Display Categories and Tasks: Displays all categories and their associated tasks.
5. Count Total Tasks: Displays the total number of tasks across all categories.