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CSE240 - Level 5: The Linked List Labyrinth

CSE240 - Level 5: The Linked List Labyrinth








CSE240: Linked List Labyrinth

Your Complete Guide to HW5





LVL 1: Structs
LVL 2: Pointers
LVL 3: Linked Lists
Boss Battles
Final Code




LEVEL 1: FORGING YOUR CHARACTER (Structs & Enums)


Before we can venture into the labyrinth, we need to define our character's attributes. In C, we use a struct to group different data types into a single "record". For this quest, our character is a studentRecord.


The `studentRecord` Blueprint


Our struct holds all the essential stats for one student. Notice how it contains character arrays for strings, an integer for the ID, and a special enum type for the school year.



struct studentRecord {
char studentName[MAX_NAME_LENGTH];
char major[MAX_NAME_LENGTH];
schoolYearType schoolYear; // This is our special Enum type!
unsigned int IDNumber;
struct studentRecord* next; // The magic pointer that links to the next character!
};

The `enum` Scroll


An enum (enumeration) is a way to create a set of named integer constants. It makes our code more readable than using magic numbers like 0, 1, 2, 3. Here, `freshman` is secretly `0`, `sophomore` is `1`, and so on.


typedef enum { freshman = 0, sophomore, junior, senior } schoolYearType;




LEVEL 2: MASTERING THE POINTER WAND (Memory Management)


Pointers are the magic wands of C. They don't hold data themselves; they hold the memory address *where* data lives. To create new student records on the fly, we must master memory allocation.


Casting `malloc()`


The malloc() spell (memory allocation) reserves a chunk of memory from the "heap". We tell it how much space we need (the size of one `studentRecord`), and it gives us back a generic pointer to that space. We then "cast" it to the correct pointer type.


// Reserve memory for one new student and get a pointer to it.
struct studentRecord* newNode = (struct studentRecord*)malloc(sizeof(struct studentRecord));

The `free()` Spell of Banishment


Memory you allocate with `malloc()` is not automatically cleaned up! If you lose the pointer to it, that memory becomes a "memory leak," draining your system's power. The free() spell is essential.…