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WGU C949 DATA STRUCTURES AND ALGORITHMS I
OBJECTIVE ASSESSMENT EXAM 100 QUESTIONS AND
CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |AGRADE
Question 121
Which data structure uses FIFO (First In First Out)?
A. Stack
B. Queue
C. Tree
D. Graph
Answer: B. Queue
Rationale: Queue processes elements in the order they were added.
Question 122
Which data structure uses LIFO (Last In First Out)?
A. Queue
B. Stack
C. Heap
D. Graph
Answer: B. Stack
Rationale: Stack removes the most recently added item first.
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Question 123
What is the time complexity of binary search?
A. O(n)
B. O(n²)
C. O(log n)
D. O(1)
Answer: C. O(log n)
Rationale: Binary search divides the search space in half each step.
Question 124
Which sorting algorithm has average case O(n log n)?
A. Bubble sort
B. Selection sort
C. Quick sort
D. Linear sort
Answer: C. Quick sort
Rationale: Quick sort performs efficiently on average.
Question 125
Which structure uses nodes with left and right children?
A. Array
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B. Stack
C. Binary tree
D. Queue
Answer: C. Binary tree
Rationale: Trees use hierarchical node relationships.
Question 126
What is the root node of a tree?
A. Last node
B. Middle node
C. Top node
D. Leaf node
Answer: C. Top node
Rationale: The root is the starting point of a tree.
Question 127
What does a hash table use to map keys?
A. Sorting
B. Hash function
C. Recursion
D. Looping
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Answer: B. Hash function
Rationale: Hash functions convert keys into indexes.
Question 128
Worst-case time complexity of bubble sort?
A. O(n log n)
B. O(n)
C. O(n²)
D. O(1)
Answer: C. O(n²)
Rationale: Nested comparisons cause quadratic growth.
Question 129
Which traversal visits root → left → right?
A. Inorder
B. Postorder
C. Preorder
D. Level order
Answer: C. Preorder
Rationale: Preorder processes root first.
Question 130
pg. 4
WGU C949 DATA STRUCTURES AND ALGORITHMS I
OBJECTIVE ASSESSMENT EXAM 100 QUESTIONS AND
CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |AGRADE
Question 121
Which data structure uses FIFO (First In First Out)?
A. Stack
B. Queue
C. Tree
D. Graph
Answer: B. Queue
Rationale: Queue processes elements in the order they were added.
Question 122
Which data structure uses LIFO (Last In First Out)?
A. Queue
B. Stack
C. Heap
D. Graph
Answer: B. Stack
Rationale: Stack removes the most recently added item first.
pg. 1
,2|Page
Question 123
What is the time complexity of binary search?
A. O(n)
B. O(n²)
C. O(log n)
D. O(1)
Answer: C. O(log n)
Rationale: Binary search divides the search space in half each step.
Question 124
Which sorting algorithm has average case O(n log n)?
A. Bubble sort
B. Selection sort
C. Quick sort
D. Linear sort
Answer: C. Quick sort
Rationale: Quick sort performs efficiently on average.
Question 125
Which structure uses nodes with left and right children?
A. Array
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B. Stack
C. Binary tree
D. Queue
Answer: C. Binary tree
Rationale: Trees use hierarchical node relationships.
Question 126
What is the root node of a tree?
A. Last node
B. Middle node
C. Top node
D. Leaf node
Answer: C. Top node
Rationale: The root is the starting point of a tree.
Question 127
What does a hash table use to map keys?
A. Sorting
B. Hash function
C. Recursion
D. Looping
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Answer: B. Hash function
Rationale: Hash functions convert keys into indexes.
Question 128
Worst-case time complexity of bubble sort?
A. O(n log n)
B. O(n)
C. O(n²)
D. O(1)
Answer: C. O(n²)
Rationale: Nested comparisons cause quadratic growth.
Question 129
Which traversal visits root → left → right?
A. Inorder
B. Postorder
C. Preorder
D. Level order
Answer: C. Preorder
Rationale: Preorder processes root first.
Question 130
pg. 4
