# Basic CS-Data Structures [Redpine Infotech Placement]: Sample Questions 1 - 2 of 4

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## Question 1

Data Structures

### Explanation

## Inorder Traversal

- Algorithm:
- Traverse the left sub tree, i.e.. . , call inorder (left-sub tree)
- Visit the root
- Traverse the right sub tree, i.e.. . , call inorder (right-sub tree)

- Uses of Inorder
- Binary search trees, inorder traversal provides nodes in non-decreasing order.
- To get nodes of BST in non-increasing order, a variation of inorder traversal where inorder traversal is reversed can be used.

## Ex

- In order travel (left, root, right) : 4, 2,5, 1,3

## Post Order

- Algorithm:
- Traverse the left sub tree, i.e.. . , call Postorder (left-sub tree)
- Traverse the right sub tree, i.e.. . , call Postorder (right-sub tree)
- Visit the root.

- Use of Postorder:
- Used to delete the tree.
- To get the postfix expression of expression tree.

## Ex

Postorder (Left, Right, Root) : 4 5 2 3 1

## Question 2

Data Structures

### Explanation

Re-entrance | Recursion |

A re-entrant function can be safely executed concurrently. | A recursive function calls upon itself until a given condition is met |

Re-entrant function does operations like protect/lock static state. | Recursive functions do not need to protect/lock access static state. |

Re-entrant function needs able to handle concurrent execution with different threads. | Recursive able to handle entry while it is running, but it access controlled manner and not other thread. |

Re-entrant recursive functions are thread-safe. | Recursive functions are not thread-safe |

Re-enter functions cannot modify static variables | Recursion functions can modify static variables. |