Stack Using Linked List vs Array Stack Trade-offs in DSA C - Build Both Approaches

Stack Using Linked List vs Array Stack Trade-offs

📖 Scenario: Imagine you are building a simple text editor that needs to keep track of undo actions. You want to use a stack to store these actions. You will explore two ways to build this stack: using an array and using a linked list. This will help you understand the trade-offs between these two methods.

🎯 Goal: You will create two stacks: one using an array and one using a linked list. You will push and pop some actions and see how the stacks behave differently.

📋 What You'll Learn

Create an array-based stack with fixed size

Create a linked list-based stack

Push three actions onto each stack

Pop one action from each stack

Print the remaining stack contents

💡 Why This Matters

🌍 Real World

Stacks are used in undo features, expression evaluation, and backtracking algorithms. Understanding different implementations helps choose the right one for your app.

💼 Career

Knowing stack implementations and their trade-offs is important for software developers, especially when optimizing for memory or speed.

1

Create an array-based stack

Create an integer array called arrayStack with size 5 and an integer variable arrayTop initialized to -1 to track the top of the stack.

DSA C

# Create an integer array called arrayStack with size 5
# Create an integer variable arrayTop initialized to -1

Hint

Think of arrayTop as the index where the last item was placed. Starting at -1 means the stack is empty.

2

Create a linked list-based stack

Define a struct called Node with an integer data and a pointer next to another Node. Then create a pointer linkedTop initialized to NULL to represent the top of the linked list stack.

DSA C

int arrayStack[5];
int arrayTop = -1;

// Define struct Node and create linkedTop pointer

Hint

The linked list stack uses nodes that point to the next node. linkedTop points to the top node.

3

Push three actions onto both stacks

Push the integers 10, 20, and 30 onto arrayStack by incrementing arrayTop and assigning the value. For the linked list stack, create new nodes with these values and link them at the top by updating linkedTop.

DSA C

int arrayStack[5];
int arrayTop = -1;

typedef struct Node {
    int data;
    struct Node* next;
} Node;

Node* linkedTop = NULL;

// Push 10, 20, 30 onto arrayStack
// Push 10, 20, 30 onto linked list stack

Hint

For the array stack, increase arrayTop before assigning. For the linked list, create new nodes and link them at the front.

4

Pop one action from each stack and print remaining contents

Pop one item from arrayStack by decreasing arrayTop. For the linked list stack, remove the top node by moving linkedTop to the next node and freeing the old top. Then print the remaining items in arrayStack from index 0 to arrayTop, and print the linked list stack items from linkedTop to the end.

DSA C

int arrayStack[5];
int arrayTop = -1;

typedef struct Node {
    int data;
    struct Node* next;
} Node;

Node* linkedTop = NULL;

// Push 10, 20, 30 onto arrayStack
arrayStack[++arrayTop] = 10;
arrayStack[++arrayTop] = 20;
arrayStack[++arrayTop] = 30;

// Push 10, 20, 30 onto linked list stack
Node* newNode;
newNode = (Node*)malloc(sizeof(Node));
newNode->data = 10;
newNode->next = linkedTop;
linkedTop = newNode;

newNode = (Node*)malloc(sizeof(Node));
newNode->data = 20;
newNode->next = linkedTop;
linkedTop = newNode;

newNode = (Node*)malloc(sizeof(Node));
newNode->data = 30;
newNode->next = linkedTop;
linkedTop = newNode;

// Pop one item from arrayStack
// Pop one item from linked list stack
// Print remaining items in arrayStack
// Print remaining items in linked list stack

Hint

Remember to decrease arrayTop to pop from the array stack. For the linked list, remove the top node and free its memory. Then print all remaining items.

Practice

1. Which of the following is a key advantage of using a linked list to implement a stack compared to using an array?

easy

A. It requires less pointer management

B. Accessing elements by index is faster

C. Memory usage is always less

D. The stack can grow dynamically without a fixed size limit

Solution

1. Step 1: Understand stack size behavior in linked list

   A linked list stack can grow or shrink dynamically because nodes are allocated as needed.

2. Step 2: Compare with array stack size limits

   An array stack has a fixed size or needs resizing, which is costly and limits capacity.

3. Final Answer:

   The stack can grow dynamically without a fixed size limit -> Option D

4. Quick Check:

   Dynamic size = Linked list stack advantage [OK]

Hint: Linked list stacks grow dynamically; arrays have fixed size [OK]

Common Mistakes:

• Thinking array stacks can grow without resizing
• Assuming linked lists use less memory always
• Confusing access speed advantages

2. Which syntax correctly declares a stack node for a linked list stack in C?

easy

A. typedef struct Node { int data; struct Node* next; } Node;

B. struct Node { int data; int next; };

C. typedef struct Node { int data; Node* next; } Node;

D. struct Node { int data; struct Node next; };

Solution

1. Step 1: Check correct pointer declaration

   The next pointer must be of type 'struct Node*' to point to the next node.

2. Step 2: Validate typedef usage

   typedef struct Node { int data; struct Node* next; } Node; correctly uses typedef and struct pointer syntax in C.

3. Final Answer:

   typedef struct Node { int data; struct Node* next; } Node; -> Option A

4. Quick Check:

   Correct pointer syntax = typedef struct Node { int data; struct Node* next; } Node; [OK]

Hint: Use 'struct Node* next;' for linked list pointers in C [OK]

Common Mistakes:

• Using 'Node* next;' without 'struct' in C
• Declaring next as int instead of pointer
• Missing typedef or incorrect struct syntax

3. What will be the output after pushing 10, 20, then 30 onto an empty linked list stack and then popping once?

medium

A. 20 -> 10 -> null

B. 30 -> 20 -> 10 -> null

C. 10 -> null

D. 20 -> null

Solution

1. Step 1: Push 10, 20, 30 onto stack

   Stack after pushes: top = 30, then 20, then 10 at bottom.

2. Step 2: Pop once removes top (30)

   After pop, top is 20, next is 10, then null.

3. Final Answer:

   20 -> 10 -> null -> Option A

4. Quick Check:

   Pop removes top = 20 -> 10 [OK]

Hint: Pop removes last pushed item; list shows remaining stack [OK]

Common Mistakes:

• Confusing push order with pop order
• Listing stack bottom first
• Forgetting pop removes top element

4. Given this array stack code snippet, what is the error?

int stack[3];
int top = -1;
void push(int x) {
  if(top == 3) {
    printf("Stack Overflow\n");
    return;
  }
  stack[++top] = x;
}

medium

A. The push function does not increment top

B. The stack array size is too large

C. The overflow condition should be 'top == 2' instead of 'top == 3'

D. The stack should be declared as a pointer

Solution

1. Step 1: Check array size and top index limits

   Array size is 3, so valid indices are 0,1,2; top max should be 2.

2. Step 2: Analyze overflow condition

   Condition 'top == 3' allows top to go out of bounds; should be 'top == 2'.

3. Final Answer:

   The overflow condition should be 'top == 2' instead of 'top == 3' -> Option C

4. Quick Check:

   Array max index = 2, overflow check must match [OK]

Hint: Array index max = size-1; check overflow accordingly [OK]

Common Mistakes:

• Checking overflow with wrong index
• Assuming top starts at 0
• Confusing array size with max index

5. Which of the following is a disadvantage of using an array-based stack compared to a linked list stack in a system with limited memory fragmentation?

hard

A. Linked list stack has slower push and pop operations

B. Array stack requires contiguous memory, which may be unavailable

C. Array stack uses more memory per element due to pointers

D. Linked list stack cannot be resized dynamically

Solution

1. Step 1: Understand memory allocation for array stacks

   Array stacks need a continuous block of memory, which can be hard to find if memory is fragmented.

2. Step 2: Compare with linked list memory allocation

   Linked lists allocate nodes separately, so they handle fragmentation better.

3. Final Answer:

   Array stack requires contiguous memory, which may be unavailable -> Option B

4. Quick Check:

   Contiguous memory need = array stack disadvantage [OK]

Hint: Arrays need continuous memory; linked lists do not [OK]

Common Mistakes:

• Thinking linked lists are slower always
• Assuming arrays use more memory per element
• Believing linked lists cannot resize dynamically