Data Structures & Algorithms for Competitive Exam Prep

Data Structures & Algorithms

Q. In which scenario would you prefer a stack over a queue?

A. When you need to process items in FIFO order
B. When you need to backtrack through previous states
C. When you need to store items for later retrieval
D. When you need to manage multiple tasks simultaneously

Solution

Stacks are ideal for backtracking scenarios, such as navigating through a maze or undoing actions in applications.

Correct Answer: B — When you need to backtrack through previous states

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Q. In which scenario would you prefer an AVL tree over a Red-Black tree?

A. When frequent insertions and deletions are expected
B. When search operations are more frequent than updates
C. When memory usage is a critical factor
D. When the tree needs to be perfectly balanced

Solution

AVL trees provide faster search times due to their stricter balancing, making them preferable when search operations are more frequent.

Correct Answer: B — When search operations are more frequent than updates

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Q. In which scenario would you prefer BFS over DFS?

A. When you need to find a path in a weighted graph
B. When you need to explore all possible paths
C. When you need the shortest path in an unweighted graph
D. When memory usage is a concern

Solution

BFS is preferred for finding the shortest path in unweighted graphs because it explores all neighbors at the present depth before moving deeper.

Correct Answer: C — When you need the shortest path in an unweighted graph

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Q. In which scenario would you prefer DFS over BFS?

A. Finding the shortest path
B. Exploring all possible paths
C. Finding the minimum spanning tree
D. Finding connected components

Solution

DFS is preferred when exploring all possible paths, such as in puzzles or games where all solutions need to be considered.

Correct Answer: B — Exploring all possible paths

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Q. In which scenario would you prefer Dijkstra's algorithm over Bellman-Ford algorithm?

A. When the graph has negative weights
B. When the graph is dense
C. When the graph has non-negative weights
D. When you need to find all paths

Solution

Dijkstra's algorithm is preferred over Bellman-Ford when the graph has non-negative weights, as it is more efficient in such cases.

Correct Answer: C — When the graph has non-negative weights

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Q. In which scenario would you prefer Dijkstra's algorithm over the Bellman-Ford algorithm?

A. When the graph has negative weight edges
B. When the graph is dense
C. When the graph has non-negative weights
D. When you need to find all pairs shortest paths

Solution

Dijkstra's algorithm is preferred when the graph has non-negative weights, as it is more efficient than Bellman-Ford in such cases.

Correct Answer: C — When the graph has non-negative weights

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Q. In which scenario would you prefer Merge Sort over Quick Sort?

A. When memory usage is a concern
B. When sorting linked lists
C. When the dataset is small
D. When the data is mostly sorted

Solution

Merge Sort is preferred for linked lists because it can be implemented without additional space for arrays.

Correct Answer: B — When sorting linked lists

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Q. In which scenario would you prefer using a queue over a stack?

A. When you need to reverse elements
B. When you need to process elements in the order they were added
C. When you need to access the last added element
D. When you need to sort elements

Solution

A queue is preferred when processing elements in the order they were added (FIFO), such as in task scheduling.

Correct Answer: B — When you need to process elements in the order they were added

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Q. In which scenario would you prefer using a Red-Black tree over an AVL tree?

A. When frequent insertions and deletions are expected
B. When memory usage is a critical factor
C. When the dataset is static
D. When search operations are the most frequent

Solution

Red-Black trees are generally preferred when there are frequent insertions and deletions because they require fewer rotations to maintain balance compared to AVL trees.

Correct Answer: A — When frequent insertions and deletions are expected

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Q. In which scenario would you prefer using an AVL tree over a Red-Black tree?

A. When frequent insertions and deletions are required.
B. When search operations are more frequent than insertions.
C. When memory usage is a concern.
D. When the tree needs to be unbalanced.

Solution

AVL trees provide faster lookups than Red-Black trees, making them preferable when search operations are more frequent.

Correct Answer: B — When search operations are more frequent than insertions.

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Q. In which scenario would you prefer using Dijkstra's algorithm over A* search algorithm?

A. When you need to find the shortest path in a grid
B. When the heuristic is not available
C. When the graph has negative weights
D. When you need to find all paths

Solution

Dijkstra's algorithm is preferred when there is no heuristic available, as A* relies on heuristics to guide its search.

Correct Answer: B — When the heuristic is not available

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Q. In which scenario would you prefer using Dijkstra's algorithm over the Bellman-Ford algorithm?

A. When the graph has negative weights
B. When the graph is dense
C. When the graph has non-negative weights
D. When you need to find all pairs shortest paths

Solution

Dijkstra's algorithm is preferred when the graph has non-negative weights, as it is more efficient in such cases compared to Bellman-Ford.

Correct Answer: C — When the graph has non-negative weights

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Q. In which scenario would you use a binary tree for data storage?

A. When data needs to be accessed in a sorted manner
B. When data is static and does not change
C. When data is accessed randomly
D. When data is sequentially processed

Solution

Binary trees are ideal for scenarios where data needs to be stored and accessed in a sorted manner, allowing for efficient searching.

Correct Answer: A — When data needs to be accessed in a sorted manner

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Q. In which scenario would you use a binary tree to represent hierarchical data?

A. File system structure
B. Social network connections
C. Web page links
D. All of the above

Solution

Binary trees can effectively represent hierarchical data structures such as file systems, where each node can represent a directory or file.

Correct Answer: A — File system structure

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Q. In which traversal method are nodes visited in ascending order for a binary search tree?

A. Pre-order
B. In-order
C. Post-order
D. Level-order

Solution

In In-order traversal of a binary search tree, nodes are visited in ascending order.

Correct Answer: B — In-order

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Q. In which traversal method are nodes visited in the order of left child, root, right child?

A. Pre-order
B. Post-order
C. In-order
D. Level-order

Solution

In In-order traversal, nodes are visited in the order of left child, root, and then right child.

Correct Answer: C — In-order

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Q. In which traversal method are nodes visited in the order of left subtree, root, right subtree?

A. In-order
B. Pre-order
C. Post-order
D. Level-order

Solution

In In-order traversal, nodes are visited in the order of left subtree, root, and then right subtree.

Correct Answer: A — In-order

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Q. In which traversal method are nodes visited level by level?

A. In-order
B. Post-order
C. Pre-order
D. Level-order

Solution

Level-order traversal visits nodes level by level, starting from the root.

Correct Answer: D — Level-order

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Q. In which traversal method do you visit the left subtree, then the root, and finally the right subtree?

A. Pre-order
B. In-order
C. Post-order
D. Level-order

Solution

In In-order traversal, the left subtree is visited first, followed by the root node, and then the right subtree.

Correct Answer: B — In-order

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Q. What color is the root node of a Red-Black tree?

A. Red
B. Black
C. It can be either
D. None of the above

Solution

The root node of a Red-Black tree is always black, which helps maintain the properties of the tree.

Correct Answer: B — Black

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Q. What condition must be met for Dijkstra's algorithm to work correctly?

A. All edge weights must be positive
B. The graph must be a tree
C. All nodes must be connected
D. The graph must be directed

Solution

Dijkstra's algorithm requires that all edge weights be non-negative to ensure that the shortest path is correctly identified.

Correct Answer: A — All edge weights must be positive

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Q. What data structure is commonly used to implement Dijkstra's algorithm efficiently?

A. Array
B. Linked List
C. Priority Queue
D. Stack

Solution

A priority queue is used in Dijkstra's algorithm to efficiently retrieve the next node with the smallest tentative distance.

Correct Answer: C — Priority Queue

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Q. What data structure is commonly used to implement Dijkstra's algorithm?

A. Array
B. Stack
C. Priority Queue
D. Linked List

Solution

A priority queue is commonly used in Dijkstra's algorithm to efficiently retrieve the next node with the smallest tentative distance.

Correct Answer: C — Priority Queue

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Q. What data structure is commonly used to implement the priority queue in Dijkstra's algorithm?

A. Array
B. Linked List
C. Binary Heap
D. Stack

Solution

A binary heap is commonly used to implement the priority queue in Dijkstra's algorithm, allowing efficient extraction of the minimum element.

Correct Answer: C — Binary Heap

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Q. What data structure is typically used to implement BFS?

A. Stack
B. Queue
C. Linked List
D. Array

Solution

BFS uses a queue to keep track of the vertices that need to be explored next, ensuring that vertices are processed in the order they are discovered.

Correct Answer: B — Queue

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Q. What data structure is typically used to implement Dijkstra's algorithm efficiently?

A. Array
B. Linked List
C. Priority Queue
D. Stack

Solution

A priority queue is used in Dijkstra's algorithm to efficiently retrieve the next node with the smallest tentative distance.

Correct Answer: C — Priority Queue

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Q. What data structure is used to implement a breadth-first search (BFS)?

A. Stack
B. Queue
C. Array
D. Linked List

Solution

A queue is used to implement breadth-first search (BFS) as it processes nodes in a first-in, first-out (FIFO) manner.

Correct Answer: B — Queue

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Q. What data structure would you use to implement a printer queue?

A. Stack
B. Queue
C. Linked List
D. Array

Solution

A queue is used for printer queues because it processes print jobs in the order they are received (FIFO).

Correct Answer: B — Queue

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Q. What does BFS stand for in graph traversal?

A. Binary First Search
B. Breadth First Search
C. Best First Search
D. Backtracking First Search

Solution

BFS stands for Breadth First Search, which is an algorithm for traversing or searching tree or graph data structures.

Correct Answer: B — Breadth First Search

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Q. What happens if binary search is applied to a linked list?

A. It works efficiently
B. It cannot be applied
C. It works but is inefficient
D. It requires additional data structures

Solution

Binary search cannot be efficiently applied to a linked list because it requires random access to elements, which linked lists do not provide.

Correct Answer: C — It works but is inefficient

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Data Structures & Algorithms

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