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Whether you’re a beginner or an experienced developer, preparation is key to cracking coding interviews. This page will help you prepare for the Top 100 coding interview questions. With practice and the right mindset, you can approach each question with confidence.
Here, you’ll find problems on topics like data structures, algorithms, loops, arrays, and more. Practicing these questions will help you build confidence and improve your problem-solving skills.
Whether you’re prepping for a big tech company or a startup, these questions will sharpen your skills and boost your confidence.
Answer:
A data structure is a storage format that defines the way data is stored, organized, and manipulated. Some popular data structures are Arrays, Trees, and Graphs.
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- An array is commonly referred to as a collection of items stored at contiguous memory locations.
- Items stored are of the same type.
- It organizes data so that a related set of values can be easily sorted or searched.
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- Like an array, a linked list refers to a linear data structure in which the elements are not necessarily stored in a contiguous manner.
- It is basically a sequence of nodes, each node points towards the next node forming a chain-like structure.
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- A stack refers to a linear data structure performing operations in a LIFO (Last In First Out) order.
- In a stack, elements can only be accessed, starting from the topmost to the bottom element.
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- LIFO is an abbreviation for Last In First Out
- It is a way of accessing, storing and retrieving data.
- It extracts the data that was stored last first.
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- FIFO stands for First In First Out.
- It is a way of accessing, storing and retrieving data.
- The data that was stored first is extracted first.
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- A queue refers to a linear data structure that performs operations in a FIFO order.
- In a queue, the least recently added elements are removed first as opposed to a stack.
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- A binary tree is an extension of the linked list structure where each node has at most two children.
- A binary tree has two nodes at all times, a left node and a right node.
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- Recursion refers to a function calling itself based on a terminating condition.
- It uses LIFO and therefore makes use of the stack data structure.
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OOPs stands for Object-Oriented Programming System, a paradigm that provides concepts such as objects, classes, and inheritance.
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Following are the concepts introduced in OOPs:
Object – A real-world entity having a particular state and behavior. We can define it as an instance of a class.
Class – A logical entity that defines the blueprint from which an object can be created or instantiated.
Inheritance – A concept that refers to an object gaining all the properties and behaviors of a parent object. It provides code reusability.
Polymorphism – A concept that allows a task to be performed in different ways. In Java, we use method overloading and method overriding to achieve polymorphism.
Abstraction – A concept that hides the internal details of an application and only shows the functionality. In Java, we use abstract class and interface to achieve abstraction.
Encapsulation – A concept that refers to the wrapping of code and data together into a single unit.
Answer:
- A binary search tree is used to store data in a manner that it can be retrieved very efficiently.
- The left sub-tree contains nodes whose keys are less than the node’s key value.
- The right sub-tree contains nodes whose keys are greater than or equal to the node’s key value.
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- Doubly linked lists are categorized as a special type of linked list in which traversal across the data elements can be done in both directions.
- This is made possible by the presence of two links in every node, one that links to the node next to it and another that connects to the node before it.
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- A graph is a particular type of data structure that contains a set of ordered pairs.
- The ordered pairs in a graph are also known as edges or arcs and are most commonly used to connect nodes where the data can be stored and retrieved.
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- In linear structure, data elements are adjacent to each other. In non-linear data structure, element can connect to over two adjacent data elements.
- Examples of linear data structure include linked lists, arrays, queues, and stacks. Examples of non-linear data structure include graphs and trees.
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- A deque is a double-ended queue.
- This is a structure in which elements can be inserted or removed from either end.
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Stack follows a Last In First Out (LIFO) pattern. What this means is that data access necessarily follows a particular sequence where the last data to be stored is the first one that will be extracted. On the other hand, Arrays do not follow a specific order, but instead can be accessed or called by referring to the indexed element within the array.
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- The amount of memory that is to be reserved or allocated depends on the data type being stored in that variable.
- For example, if a variable is declared to be “integer type”, 32 bits of memory storage will then be reserved for that particular variable.
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Dynamic data structures have the feature where they expand and contract as a program runs. It provides a very flexible method of data manipulation because adjusts based on the size of the data to be manipulated.
Answer:
To get the matching characters in a string, the below steps are followed:
- Hash Map data structure is taken which works with the key-value pair.
- Loop the strings, character by character, and verify if that character of the string exists in the hash map or not.
- If the result is true, the counter for the character in the hash map is increased or else then put a count as 1.
- Once the loop ends, then the Hash map is traversed and print the characters with more than 1 count.