WGU C949 Objective Assessment Prep - Data Structures and Algorithms I
WGU C949 OBJECTIVE ASSESSMENT (Latest
2026/2027)
Data Structures and Algorithms I
Version 1 | Questions and Verified Answers | 100% Correct | Grade A
Section Questions Competency Weight
Section 1: Data Types (Primitive Types, Abstract Data
Q1 - Q25 36%
Types, Classes, and Type Systems)
Section 2: Data Structures (Arrays, Linked Lists, Stacks,
Q26 - Q45 30%
Queues, Trees, Hash Tables, Heaps, and Graphs)
Section 3: Algorithms (Searching, Sorting, Recursion,
Q46 - Q70 34%
Iteration, and Algorithm Design)
Total 70 100%
Cognitive level mix: 30% recall, 45% application, 25% analysis. Format: multiple choice, four options (A-D), one best answer.
Each question is followed by its verified answer, marked [CORRECT], and a detailed rationale with complexity analysis.
SECTION 1: DATA TYPES
Primitive Types, Abstract Data Types, Classes, and Type Systems | WGU competency weight: 36%
Q1. Which of the following is a primitive data type?
A. Stack - a LIFO collection with push and pop operations
B. Integer - a built-in numeric type such as 42 [CORRECT]
C. Linked List - a collection of nodes connected by references
D. Queue - a FIFO collection with enqueue and dequeue operations
Correct Answer: B
Rationale: An integer is a primitive (built-in) data type provided directly by the language and stores a single
atomic value. Stacks, queues, and linked lists are Abstract Data Types (ADTs) - they are higher-level containers
that must be constructed from primitive types and other structures, so options A, C, and D are composite rather
than primitive.
Version 1 | Questions and Verified Answers | Grade A Page 1
,WGU C949 Objective Assessment Prep - Data Structures and Algorithms I
Q2. In data structures terminology, what does an Abstract Data Type (ADT) specify?
A. The exact memory layout and byte ordering required for storage
B. The specific programming language in which the structure must be written
C. A set of values and the operations that can be performed on those values, without specifying how
they are implemented [CORRECT]
D. The guaranteed worst-case time complexity of every operation
Correct Answer: C
Rationale: An ADT is a logical description of WHAT a container does - its allowed values and operations - while
deliberately hiding HOW those operations work. The implementation (array vs. linked nodes) is left to the data
structure, which is why the memory-layout and language choices in A and B are wrong. ADTs also make no
complexity guarantees (D); performance depends entirely on the chosen implementation.
Q3. A developer calls list_add(item) and list_remove(item) on a collection. The documentation never
mentions whether the list uses an array or linked nodes internally. Which fundamental concept does this
illustrate?
A. Abstraction - the ADT interface exposes operations while hiding the underlying implementation
[CORRECT]
B. Recursion - the list calls itself to locate elements
C. Polymorphism - the list takes many forms at compile time
D. Instantiation - the list is copied into an object at runtime
Correct Answer: A
Rationale: Hiding the storage mechanism behind a stable operation set is precisely the abstraction an ADT
provides. Recursion (B) describes self-referential function calls, and instantiation (D) is object creation - neither
addresses implementation hiding. Because the interface stays fixed regardless of internals, the developer can use
the collection correctly without implementation knowledge.
Q4. Which group contains ONLY Abstract Data Types?
A. Integer, float, boolean, character
B. Array, integer, float, string
C. Character, boolean, pointer, integer
D. List, stack, queue, map [CORRECT]
Correct Answer: D
Rationale: List, stack, queue, and map are all classic ADTs - each is defined by its operations (positional access,
push/pop, enqueue/dequeue, key-based lookup) rather than by a storage scheme. Options A and C list primitive
types, and option B mixes the array (a raw storage structure) with primitive types. Only D contains exclusively
abstract containers.
Version 1 | Questions and Verified Answers | Grade A Page 2
, WGU C949 Objective Assessment Prep - Data Structures and Algorithms I
Q5. The Last-In-First-Out (LIFO) principle is the defining behavior of which ADT?
A. Queue
B. Stack [CORRECT]
C. Set
D. Bag
Correct Answer: B
Rationale: A stack removes its most recently added element first, which is exactly Last-In-First-Out. A queue
(A) enforces the opposite order, First-In-First-Out, while sets and bags (C, D) are unordered collections with no
positional removal discipline at all. LIFO ordering is also why stacks model undo history and function call stacks.
Q6. A print server processes documents in exactly the order they were submitted: the oldest job always prints
first. Which ADT's principle does this follow?
A. Stack, because jobs accumulate vertically
B. Heap, because priority determines order
C. Queue, because the First-In-First-Out principle serves the earliest arrival first [CORRECT]
D. Map, because each job has a unique identifier
Correct Answer: C
Rationale: Serving the oldest arrival first is First-In-First-Out behavior, the defining principle of a queue with
enqueue at the rear and dequeue at the front. A stack (A) would print the newest job first, and a heap (B) would
serve by priority rather than arrival time. A map (D) stores key-value associations and has no service order.
Q7. A student writes: "A stack is an abstract data type, while an array-based implementation of that stack is a
data structure." Is this statement correct?
A. Correct - the stack ADT defines push/pop behavior abstractly, and the array-backed version is one
concrete data structure realizing it [CORRECT]
B. Incorrect - a stack and an array are both primitive types
C. Incorrect - 'abstract data type' and 'data structure' are exact synonyms
D. Incorrect - a stack can only ever be implemented using a linked list
Correct Answer: A
Rationale: The statement correctly separates specification (the stack ADT: push, pop, peek) from realization (an
array with a top index, or equivalently a linked list). A stack is certainly not a primitive type (B), and ADT vs. data
structure is the standard specification-vs-implementation distinction, not synonymy (C). D is false because
array-based stacks are extremely common - both realizations are legitimate data structures.
Version 1 | Questions and Verified Answers | Grade A Page 3
WGU C949 OBJECTIVE ASSESSMENT (Latest
2026/2027)
Data Structures and Algorithms I
Version 1 | Questions and Verified Answers | 100% Correct | Grade A
Section Questions Competency Weight
Section 1: Data Types (Primitive Types, Abstract Data
Q1 - Q25 36%
Types, Classes, and Type Systems)
Section 2: Data Structures (Arrays, Linked Lists, Stacks,
Q26 - Q45 30%
Queues, Trees, Hash Tables, Heaps, and Graphs)
Section 3: Algorithms (Searching, Sorting, Recursion,
Q46 - Q70 34%
Iteration, and Algorithm Design)
Total 70 100%
Cognitive level mix: 30% recall, 45% application, 25% analysis. Format: multiple choice, four options (A-D), one best answer.
Each question is followed by its verified answer, marked [CORRECT], and a detailed rationale with complexity analysis.
SECTION 1: DATA TYPES
Primitive Types, Abstract Data Types, Classes, and Type Systems | WGU competency weight: 36%
Q1. Which of the following is a primitive data type?
A. Stack - a LIFO collection with push and pop operations
B. Integer - a built-in numeric type such as 42 [CORRECT]
C. Linked List - a collection of nodes connected by references
D. Queue - a FIFO collection with enqueue and dequeue operations
Correct Answer: B
Rationale: An integer is a primitive (built-in) data type provided directly by the language and stores a single
atomic value. Stacks, queues, and linked lists are Abstract Data Types (ADTs) - they are higher-level containers
that must be constructed from primitive types and other structures, so options A, C, and D are composite rather
than primitive.
Version 1 | Questions and Verified Answers | Grade A Page 1
,WGU C949 Objective Assessment Prep - Data Structures and Algorithms I
Q2. In data structures terminology, what does an Abstract Data Type (ADT) specify?
A. The exact memory layout and byte ordering required for storage
B. The specific programming language in which the structure must be written
C. A set of values and the operations that can be performed on those values, without specifying how
they are implemented [CORRECT]
D. The guaranteed worst-case time complexity of every operation
Correct Answer: C
Rationale: An ADT is a logical description of WHAT a container does - its allowed values and operations - while
deliberately hiding HOW those operations work. The implementation (array vs. linked nodes) is left to the data
structure, which is why the memory-layout and language choices in A and B are wrong. ADTs also make no
complexity guarantees (D); performance depends entirely on the chosen implementation.
Q3. A developer calls list_add(item) and list_remove(item) on a collection. The documentation never
mentions whether the list uses an array or linked nodes internally. Which fundamental concept does this
illustrate?
A. Abstraction - the ADT interface exposes operations while hiding the underlying implementation
[CORRECT]
B. Recursion - the list calls itself to locate elements
C. Polymorphism - the list takes many forms at compile time
D. Instantiation - the list is copied into an object at runtime
Correct Answer: A
Rationale: Hiding the storage mechanism behind a stable operation set is precisely the abstraction an ADT
provides. Recursion (B) describes self-referential function calls, and instantiation (D) is object creation - neither
addresses implementation hiding. Because the interface stays fixed regardless of internals, the developer can use
the collection correctly without implementation knowledge.
Q4. Which group contains ONLY Abstract Data Types?
A. Integer, float, boolean, character
B. Array, integer, float, string
C. Character, boolean, pointer, integer
D. List, stack, queue, map [CORRECT]
Correct Answer: D
Rationale: List, stack, queue, and map are all classic ADTs - each is defined by its operations (positional access,
push/pop, enqueue/dequeue, key-based lookup) rather than by a storage scheme. Options A and C list primitive
types, and option B mixes the array (a raw storage structure) with primitive types. Only D contains exclusively
abstract containers.
Version 1 | Questions and Verified Answers | Grade A Page 2
, WGU C949 Objective Assessment Prep - Data Structures and Algorithms I
Q5. The Last-In-First-Out (LIFO) principle is the defining behavior of which ADT?
A. Queue
B. Stack [CORRECT]
C. Set
D. Bag
Correct Answer: B
Rationale: A stack removes its most recently added element first, which is exactly Last-In-First-Out. A queue
(A) enforces the opposite order, First-In-First-Out, while sets and bags (C, D) are unordered collections with no
positional removal discipline at all. LIFO ordering is also why stacks model undo history and function call stacks.
Q6. A print server processes documents in exactly the order they were submitted: the oldest job always prints
first. Which ADT's principle does this follow?
A. Stack, because jobs accumulate vertically
B. Heap, because priority determines order
C. Queue, because the First-In-First-Out principle serves the earliest arrival first [CORRECT]
D. Map, because each job has a unique identifier
Correct Answer: C
Rationale: Serving the oldest arrival first is First-In-First-Out behavior, the defining principle of a queue with
enqueue at the rear and dequeue at the front. A stack (A) would print the newest job first, and a heap (B) would
serve by priority rather than arrival time. A map (D) stores key-value associations and has no service order.
Q7. A student writes: "A stack is an abstract data type, while an array-based implementation of that stack is a
data structure." Is this statement correct?
A. Correct - the stack ADT defines push/pop behavior abstractly, and the array-backed version is one
concrete data structure realizing it [CORRECT]
B. Incorrect - a stack and an array are both primitive types
C. Incorrect - 'abstract data type' and 'data structure' are exact synonyms
D. Incorrect - a stack can only ever be implemented using a linked list
Correct Answer: A
Rationale: The statement correctly separates specification (the stack ADT: push, pop, peek) from realization (an
array with a top index, or equivalently a linked list). A stack is certainly not a primitive type (B), and ADT vs. data
structure is the standard specification-vs-implementation distinction, not synonymy (C). D is false because
array-based stacks are extremely common - both realizations are legitimate data structures.
Version 1 | Questions and Verified Answers | Grade A Page 3
