# Data Structure Interview Questions and Answers For Freshers Part-3

**21. Mention some of the problem solving strategies?**

The most widely strategies are listed below

i)Divide and conquer

ii)Binary doubling strategy

iii)Dynamic programming

**22. What is divide and conquer method?**

The basic idea is to divide the problem into several sub problems beyond which cannot be further subdivided. Then solve the sub problems efficiently and join then together to get the solution for the main problem.

**23. What is the need for the header?**

Header of the linked list is the first element in the list and it stores the number of elements in the list. It points to the first data element of the list.

**24. Define leaf?**

In a directed tree any node which has out degree o is called a terminal node or a leaf.

**25. What are the applications of binary tree?**

Binary tree is used in data processing.

**26. What are the different types of traversing?**

The different types of traversing are

i)Pre-order traversal-yields prefix from of expression.

ii)In-order traversal-yields infix form of expression.

iii)Post-order traversal-yields postfix from of expression.

**27. Define pre-order traversal?**

i)Process the root node

ii)Process the left subtree

iii)Process the right subtree

**28. Define post-order traversal?**

i)Process the left subtree

ii)Process the right subtree

iii)Process the root node

**29. Define in -order traversal?**

i)Process the left subtree

ii)Process the root node

iii)Process the right subtree

**30. What is meant by sorting?**

Ordering the data in an increasing or decreasing fashion according to some relationship among the data item is called sorting.

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