Stack Using Linked List vs Array Stack Trade-offs in DSA C - Complexity Comparison

Time Complexity: Stack Using Linked List vs Array Stack Trade-offs

O(1)

Understanding Time Complexity

We want to understand how fast stack operations run when using a linked list versus an array.

Which method is faster or slower as the stack grows?

Scenario Under Consideration

Analyze the time complexity of push and pop operations in these stack implementations.

// Array Stack Push
void push(int val) {
  if (top == capacity - 1) return; // stack full
  arr[++top] = val;
}

// Linked List Stack Push
void push(Node** head, int val) {
  Node* newNode = (Node*)malloc(sizeof(Node));
  newNode->data = val;
  newNode->next = *head;
  *head = newNode;
}
    

These snippets show adding an item to the stack using array and linked list.

Identify Repeating Operations

Both push and pop do a fixed number of steps each time.

• Primary operation: Assigning or updating pointers or array indexes.
• How many times: Exactly once per push or pop call, no loops involved.

How Execution Grows With Input

Each push or pop takes the same amount of work no matter how big the stack is.

Input Size (n)	Approx. Operations per push/pop
10	5 steps
100	5 steps
1000	5 steps

Pattern observation: The work stays the same as the stack grows.

Final Time Complexity

Time Complexity: O(1)

This means each push or pop operation takes the same short time no matter how many items are in the stack.

Common Mistake

[X] Wrong: "Linked list push is slower because it uses pointers and memory allocation."

[OK] Correct: While linked list push uses memory allocation, the actual steps to add or remove are constant time, just like array push if no resizing is needed.

Interview Connect

Knowing these trade-offs helps you explain why you might choose one stack type over another in real projects.

Self-Check

"What if the array stack needs to resize when full? How would that affect the time complexity of push?"