Which of the following cipher is formed by applying columnar transposition cipher twice?

Which data structure is used to implement a binary heap efficiently?

A. Array

B. Linked List

C. Stack

D. Queue

In which scenario would you use a Bloom Filter?

A. For implementing a stack-based algorithm

B. To maintain a balanced binary tree

C. For efficient sorting of elements

D. To test membership in a large dataset

What data structure is used for implementing an efficient priority queue with multiple priority levels?

A. Queue

B. Stack

C. Heap

D. Array

Which data structure is best for implementing a sparse matrix?

A. Array

B. Hash Map

C. Trie

D. Array