WGU - C949 Exam UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS
Array - CORRECT ANSWER A data structure that stores an ordered list of items, with each
item is directly accessible by a positional index.
Linked List - CORRECT ANSWER A data structure that stores ordered list of items in nodes,
where each node stores data and has a pointer to the next node.
Bianary Search Tree - CORRECT ANSWER A data structure in which each node stores data
and has up to two children, known as a left child and a right child.
Hash Table - CORRECT ANSWER A data structure that stores unordered items by mapping
(or hashing) each item to a location in an array (or vector).
Hashing - CORRECT ANSWER mapping each item to a location in an array (in a hash table).
Chaining - CORRECT ANSWER handles hash table collisions by using a list for each bucket,
where each list may store multiple items that map to the same bucket.
Hash key - CORRECT ANSWER value used to map an index
bucket - CORRECT ANSWER each array element in a hash table
ie A 100 elements hash table has 100 buckets
modulo hash function - CORRECT ANSWER computes a bucket index from the items key.
It will map (num_keys / num_buckets) keys to each bucket.
ie... keys range 0 to 49 will have 5 keys per bucket.
= 5
hash table searching - CORRECT ANSWER Hash tables support fast search, insert, and
remove.
,Requires on average O(1)
Linear search requires O(N)
modulo operator % - CORRECT ANSWER common has function uses this. which computes
the integer remainder when dividing two numbers.
Ex: For a 20 element hash table, a hash function of key % 20 will map keys to bucket indices 0 to 19.
Max-Heap - CORRECT ANSWER A binary tree that maintains the simple property that a
node's key is greater than or equal to the node's childrens' keys. (Actually, a max-heap may be any
tree, but is commonly a binary tree).
*a max-heap's root always has the maximum key in the entire tree.
Heap storage - CORRECT ANSWER Heaps are typically stored using arrays. Given a tree
representation of a heap, the heap's array form is produced by traversing the tree's levels from left to
right and top to bottom. The root node is always the entry at index 0 in the array, the root's left child is
the entry at index 1, the root's right child is the entry at index 2, and so on.
Max-heap insert - CORRECT ANSWER An insert into a max-heap starts by inserting the node
in the tree's last level, and then swapping the node with its parent until no max-heap property violation
occurs.
The upward movement of a node in a max-heap is sometime called percolating.
Complexity O(logN)
Max-heap remove - CORRECT ANSWER Always a removal of the root, and is done by
replacing the root with the last level's last node, and swapping that node with its greatest child until no
max-heap property violation occurs.
Complexity O(logN)
Percolating - CORRECT ANSWER The upward movement of a node in a max-heap
Min-Heap - CORRECT ANSWER Similar to a max-heap, but a node's key is less than or equal
to its children's keys.
, Heap - Parent and child indices - CORRECT ANSWER Because heaps are not implemented
with node structures and parent/child pointers, traversing from a node to parent or child nodes
requires referring to nodes by index. The table below shows parent and child index formulas for a
heap.
ie
1) parent index for node at index 12? 5
*** ((12-1) // 2) = 5 or 12 //2 -1 = 5
2) child indices for a node at index 6? 13 & 14
*** 2 * 6 + 1 = 13 and 2 * 6 + 2 = 14
**Double# and add 1, double# and add 2
Node index Parent Index Child Indices
0 N/A 1, 2
1 0 3, 4
2 0 5, 6
3 1 7, 8
4 1 9, 10
5 2 11, 12
Heap - parent_index - CORRECT ANSWER parent_index = (node_index - 1) // 2
or node_index // 2 - 1
Heap - left_child_index - CORRECT ANSWER left_child_index = 2 * node_index + 1
Heap - right_child_index - CORRECT ANSWER right_child_index = 2 * node_index + 2
Implementing priority queues with heaps. - CORRECT ANSWER Both functions return the
value in the root, but the Pop function removes the value and the Peek function does not. Pop is worst-
case O(logN) and Peek is worst-case O(1).
QUESTIONS AND CORRECT ANSWERS
Array - CORRECT ANSWER A data structure that stores an ordered list of items, with each
item is directly accessible by a positional index.
Linked List - CORRECT ANSWER A data structure that stores ordered list of items in nodes,
where each node stores data and has a pointer to the next node.
Bianary Search Tree - CORRECT ANSWER A data structure in which each node stores data
and has up to two children, known as a left child and a right child.
Hash Table - CORRECT ANSWER A data structure that stores unordered items by mapping
(or hashing) each item to a location in an array (or vector).
Hashing - CORRECT ANSWER mapping each item to a location in an array (in a hash table).
Chaining - CORRECT ANSWER handles hash table collisions by using a list for each bucket,
where each list may store multiple items that map to the same bucket.
Hash key - CORRECT ANSWER value used to map an index
bucket - CORRECT ANSWER each array element in a hash table
ie A 100 elements hash table has 100 buckets
modulo hash function - CORRECT ANSWER computes a bucket index from the items key.
It will map (num_keys / num_buckets) keys to each bucket.
ie... keys range 0 to 49 will have 5 keys per bucket.
= 5
hash table searching - CORRECT ANSWER Hash tables support fast search, insert, and
remove.
,Requires on average O(1)
Linear search requires O(N)
modulo operator % - CORRECT ANSWER common has function uses this. which computes
the integer remainder when dividing two numbers.
Ex: For a 20 element hash table, a hash function of key % 20 will map keys to bucket indices 0 to 19.
Max-Heap - CORRECT ANSWER A binary tree that maintains the simple property that a
node's key is greater than or equal to the node's childrens' keys. (Actually, a max-heap may be any
tree, but is commonly a binary tree).
*a max-heap's root always has the maximum key in the entire tree.
Heap storage - CORRECT ANSWER Heaps are typically stored using arrays. Given a tree
representation of a heap, the heap's array form is produced by traversing the tree's levels from left to
right and top to bottom. The root node is always the entry at index 0 in the array, the root's left child is
the entry at index 1, the root's right child is the entry at index 2, and so on.
Max-heap insert - CORRECT ANSWER An insert into a max-heap starts by inserting the node
in the tree's last level, and then swapping the node with its parent until no max-heap property violation
occurs.
The upward movement of a node in a max-heap is sometime called percolating.
Complexity O(logN)
Max-heap remove - CORRECT ANSWER Always a removal of the root, and is done by
replacing the root with the last level's last node, and swapping that node with its greatest child until no
max-heap property violation occurs.
Complexity O(logN)
Percolating - CORRECT ANSWER The upward movement of a node in a max-heap
Min-Heap - CORRECT ANSWER Similar to a max-heap, but a node's key is less than or equal
to its children's keys.
, Heap - Parent and child indices - CORRECT ANSWER Because heaps are not implemented
with node structures and parent/child pointers, traversing from a node to parent or child nodes
requires referring to nodes by index. The table below shows parent and child index formulas for a
heap.
ie
1) parent index for node at index 12? 5
*** ((12-1) // 2) = 5 or 12 //2 -1 = 5
2) child indices for a node at index 6? 13 & 14
*** 2 * 6 + 1 = 13 and 2 * 6 + 2 = 14
**Double# and add 1, double# and add 2
Node index Parent Index Child Indices
0 N/A 1, 2
1 0 3, 4
2 0 5, 6
3 1 7, 8
4 1 9, 10
5 2 11, 12
Heap - parent_index - CORRECT ANSWER parent_index = (node_index - 1) // 2
or node_index // 2 - 1
Heap - left_child_index - CORRECT ANSWER left_child_index = 2 * node_index + 1
Heap - right_child_index - CORRECT ANSWER right_child_index = 2 * node_index + 2
Implementing priority queues with heaps. - CORRECT ANSWER Both functions return the
value in the root, but the Pop function removes the value and the Peek function does not. Pop is worst-
case O(logN) and Peek is worst-case O(1).
