WGU C949 DATA STRUCTURES AND ALGORITHMS I
PRACTICE EXAM|QUESTIONS AND ANSWER WITH
RATIONALE|2026 UPDATE|100% PASS
1. Which ADT allows access to elements using a specific index?
A) Bag
B) Stack
C) List
D) Queue
Answer: C) List
Rationale: A List is an ordered collection where each element can be accessed
directly using its index or position. This is a defining characteristic of the List ADT .
2. Which ADT follows a Last-In-First-Out (LIFO) pattern?
A) Queue
B) Stack
C) List
D) Bag
Answer: B) Stack
,Rationale: A Stack removes elements in reverse order of insertion, adhering to the
LIFO principle where the most recently added item is the first to be removed .
3. Which ADT allows duplicate elements without a defined order or indexing?
A) List
B) Bag
C) Stack
D) Queue
Answer: B) Bag
Rationale: A Bag is an unordered collection that permits duplicate elements but
does not provide positional access or any specific ordering .
4. What is the definition of an Abstract Data Type (ADT)?
A) A concrete implementation of a data structure
B) A data type described by predefined user operations without indication of how
each operation is implemented
C) A programming language feature
D) A specific data structure like an array or linked list
Answer: B) A data type described by predefined user operations without
indication of how each operation is implemented
Rationale: An ADT defines the behavior of a data type from the user's perspective,
specifying operations but hiding implementation details .
,5. Which ADT is a collection of distinct items with no duplicates allowed?
A) Bag
B) Queue
C) Set
D) List
Answer: C) Set
Rationale: A Set is an ADT designed for collections of unique items, where
duplicates are not permitted. Common underlying data structures include binary
search trees and hash tables .
6. Which ADT allows insertion at one end and removal from the other end?
A) Stack
B) Queue
C) Deque
D) Priority Queue
Answer: B) Queue
Rationale: A Queue follows the FIFO (First-In-First-Out) principle where items are
inserted at the back (enqueue) and removed from the front (dequeue) .
7. What is a priority queue?
A) A queue where items are processed in random order
, B) A queue where each item has a priority, and items with higher priority are
closer to the front than items with lower priority
C) A queue that only stores priority numbers
D) A stack with priority ordering
Answer: B) A queue where each item has a priority, and items with higher priority
are closer to the front than items with lower priority
Rationale: In a priority queue, elements have associated priorities, and higher-
priority elements are removed before lower-priority ones. Common underlying
data structures include heaps .
8. Which ADT associates keys with values?
A) List
B) Stack
C) Dictionary (Map)
D) Queue
Answer: C) Dictionary (Map)
Rationale: A dictionary or map ADT stores key-value pairs, allowing efficient
retrieval of values based on their associated keys. Keys are typically unique and
immutable .
9. What is a characteristic of keys in an associative dictionary data type?
A) They can be changed after creation
B) They are unique and immutable
PRACTICE EXAM|QUESTIONS AND ANSWER WITH
RATIONALE|2026 UPDATE|100% PASS
1. Which ADT allows access to elements using a specific index?
A) Bag
B) Stack
C) List
D) Queue
Answer: C) List
Rationale: A List is an ordered collection where each element can be accessed
directly using its index or position. This is a defining characteristic of the List ADT .
2. Which ADT follows a Last-In-First-Out (LIFO) pattern?
A) Queue
B) Stack
C) List
D) Bag
Answer: B) Stack
,Rationale: A Stack removes elements in reverse order of insertion, adhering to the
LIFO principle where the most recently added item is the first to be removed .
3. Which ADT allows duplicate elements without a defined order or indexing?
A) List
B) Bag
C) Stack
D) Queue
Answer: B) Bag
Rationale: A Bag is an unordered collection that permits duplicate elements but
does not provide positional access or any specific ordering .
4. What is the definition of an Abstract Data Type (ADT)?
A) A concrete implementation of a data structure
B) A data type described by predefined user operations without indication of how
each operation is implemented
C) A programming language feature
D) A specific data structure like an array or linked list
Answer: B) A data type described by predefined user operations without
indication of how each operation is implemented
Rationale: An ADT defines the behavior of a data type from the user's perspective,
specifying operations but hiding implementation details .
,5. Which ADT is a collection of distinct items with no duplicates allowed?
A) Bag
B) Queue
C) Set
D) List
Answer: C) Set
Rationale: A Set is an ADT designed for collections of unique items, where
duplicates are not permitted. Common underlying data structures include binary
search trees and hash tables .
6. Which ADT allows insertion at one end and removal from the other end?
A) Stack
B) Queue
C) Deque
D) Priority Queue
Answer: B) Queue
Rationale: A Queue follows the FIFO (First-In-First-Out) principle where items are
inserted at the back (enqueue) and removed from the front (dequeue) .
7. What is a priority queue?
A) A queue where items are processed in random order
, B) A queue where each item has a priority, and items with higher priority are
closer to the front than items with lower priority
C) A queue that only stores priority numbers
D) A stack with priority ordering
Answer: B) A queue where each item has a priority, and items with higher priority
are closer to the front than items with lower priority
Rationale: In a priority queue, elements have associated priorities, and higher-
priority elements are removed before lower-priority ones. Common underlying
data structures include heaps .
8. Which ADT associates keys with values?
A) List
B) Stack
C) Dictionary (Map)
D) Queue
Answer: C) Dictionary (Map)
Rationale: A dictionary or map ADT stores key-value pairs, allowing efficient
retrieval of values based on their associated keys. Keys are typically unique and
immutable .
9. What is a characteristic of keys in an associative dictionary data type?
A) They can be changed after creation
B) They are unique and immutable
