# Data structure & Algorithm Interview Questions

### 1) What is Data Structure?

Data structure is a way of storing, collecting and organizing data into the main memory. It makes data access more efficient and increase performance.

Array, List, Queue are some important data structures.

### 2) How many types of Data Structure.

There are 2 types of Data Structure:

Primitive- It is a basic data structure that directly operate the machine instructions.

Integer, Floating point numbers, Character constants, String constants and Pointer they are in primitive data structure.

Non-primitive- It is a more complicated data structure and are derived from primitive data structures.

Arrays, Lists and Files these are in Non-primitive category.

### 3) What is Algorithm?

Algorithm is a process of solving problem in step by step manner. It is a procedure or formula that can be used to solve a problem. It is initial step of starting and implementing programming code.

### 4) What is linked list?

It is a sequence of nodes in which each node contains a pointer that points to another node. The entry point into a linked list is called the head of the list and last node is called tail node.

### 5) What is LIFO?

LIFO (Last In First Out) is a manner to store and access elements into a data structure. In LIFO, data which was stored in the last, should be extract first. It means, the last inserted element will be accessed first.

### 6) What is queue?

Queue is a data structures that is used to store data in FIFO (First In First Out). In queue data structure, new element is inserted at one end and existing element are removed from other end.

### 7) What are binary trees?

It is a type of data structure that has two nodes, left node and right node. In programming, binary trees are actually an extension of the linked list structures.

### 8) What is stack?

Stack is a data structure in which only the top elements can be accessed. As data is stored in the stack, each data pushed downwards, except the most recently added data on top.

### 9) What is Binary search tree?

It stores data in such a way that data can be retrieved very easily. The left subtree contains nodes whose keys are less then the nodeâ€™s key value, where as the right subtree contains nodes whose keys are greater than or equal to the nodeâ€™s key value.

### 10) What is multidimensional array?

An array which have more then two dimensions is called multidimensional array. It use multiple indexes to store data.

### 11) What is FIFO?

FIFO is First In, First Out. It used to represent how data is accessed in a queue. The Data which is added first in queue, it will be the first to remove.

### 12) What is ordered list?

An ordered list is a list where the items in the list are in sorted order. In ordered list, each node position in the list is determine by the value of its key component, so that the key value form an increasing order.

### 13) What is Merge sort?

Merge sort is follow the rule of divide and conquer technique. In Merge sort, it is divides the array in equal parts then combine them in sorted manner. Merge sort is quite fast and time complexity.

### 14) Differentiate between NULL and VOID.

Null is a value, a variable which is given a null value simply indicates an empty value. Void is a data type which is used to identify pointer as having no initial size.