🏗️ Basic Data Structures¶

Prerequisites: None

Beyond simple variables and arrays, data structures help organize information for efficient access and modification.

1. Stack Implementation (Array)¶

Rating: Beginner | Difficulty: Medium Implement a Stack (LIFO) using an array with push and pop operations.

💡 Hint

Use a top variable to keep track of the current index.

2. Queue Implementation (Array)¶

Rating: Beginner | Difficulty: Medium Implement a Queue (FIFO) using an array with enqueue and dequeue operations.

💡 Hint

Use front and rear variables.

3. Check for Balanced Parentheses¶

Rating: Intermediate | Difficulty: Medium Use a Stack to check if an expression like (( )) is balanced.

💡 Hint

Push ( to the stack. Pop when you see ). Stack should be empty at the end.

4. Reverse a String using Stack¶

Rating: Beginner | Difficulty: Easy Push every character of a string into a stack, then pop them all out to get the reversed string.

💡 Hint

Last In, First Out!

5. Linked List Node Creation¶

Rating: Beginner | Difficulty: Medium Create a simple structure/class for a Node in a singly linked list.

💡 Hint

A Node contains data and a pointer/reference to the next node.

6. Linked List - Insert at Beginning¶

Rating: Intermediate | Difficulty: Medium Write a function to insert a new node at the start of a singly linked list.

💡 Hint

newNode.next = head; head = newNode;

7. Linked List - Traversal¶

Rating: Beginner | Difficulty: Easy Print all elements of a singly linked list.

💡 Hint

Use a temp pointer and loop while (temp != null).

8. Stack using Linked List¶

Rating: Advanced | Difficulty: Medium Implement a Stack where each element is a node in a linked list.

💡 Hint

Pushing is inserting at the head; popping is deleting the head.

9. Queue using Linked List¶

Rating: Advanced | Difficulty: Medium Implement a Queue using a linked list.

💡 Hint

Maintain both front and rear pointers for efficient operations.

10. Circular Queue¶

Rating: Advanced | Difficulty: Hard Implement a Circular Queue to reuse empty spaces in an array.

💡 Hint

Use the modulus operator: rear = (rear + 1) % size.

11. Reverse a Linked List¶

Rating: Pro | Difficulty: Hard Reverse the links in a singly linked list so the tail becomes the head.

💡 Hint

Use three pointers: prev, current, and next.

12. Find the Middle of a Linked List¶

Rating: Advanced | Difficulty: Medium Find the middle node of a linked list in a single pass.

💡 Hint

Use two pointers: "Slow" (moves 1 step) and "Fast" (moves 2 steps).

13. Search in a Linked List¶

Rating: Beginner | Difficulty: Easy Check if a specific value exists in a linked list.

💡 Hint

Traverse and compare.

14. Delete a Node (Linked List)¶

Rating: Intermediate | Difficulty: Medium Delete a node with a specific value from a linked list.

💡 Hint

Link the previous node directly to the next node of the target.

15. Decimal to Binary using Stack¶

Rating: Intermediate | Difficulty: Medium Convert a decimal number to binary by pushing remainders onto a stack.

💡 Hint

Divide by 2, push remainder, repeat. Pop everything at the end.

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