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Mina #29

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275 changes: 150 additions & 125 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@


# Defines a node in the singly linked list
class Node
attr_reader :data # allow external entities to read value but not write
Expand All @@ -12,152 +13,176 @@ def initialize(value, next_node = nil)

# Defines the singly linked list
class LinkedList
def initialize
@head = nil # keep the head private. Not accessible outside this class
end

# method to add a new node with the specific data value in the linked list
# insert the new node at the beginning of the linked list
# Time Complexity:
# Space Complexity
def add_first(value)
raise NotImplementedError
end

# method to find if the linked list contains a node with specified value
# returns true if found, false otherwise
# Time Complexity:
# Space Complexity
def search(value)
raise NotImplementedError
end

# method to return the max value in the linked list
# returns the data value and not the node
# Time Complexity:
# Space Complexity
def find_max
raise NotImplementedError
end
def initialize
@head = nil # keep the head private. Not accessible outside this class
end

# method to return the min value in the linked list
# returns the data value and not the node
# Time Complexity:
# Space Complexity
def find_min
raise NotImplementedError
# method to add a new node with the specific data value in the linked list
# insert the new node at the beginning of the linked list
# Time Complexity: O(1) constant because adding first node
# Space Complexity: O(1) constant because adding one node
def add_first(value)
new_node = Node.new(value)
if @head != nil
new_node.next = @head
end
@head = new_node
end

# Additional Exercises
# returns the value in the first node
# returns nil if the list is empty
# Time Complexity: O(1) constant because only searching for value of head
# Space Complexity: O(1) constant because no additional space is needed
def get_first
return nil if !@head
return @head.data
end

# method that returns the length of the singly linked list
# Time Complexity:
# Space Complexity
def length
raise NotImplementedError
end
# method that returns the length of the singly linked list
# Time Complexity: O(n) where n equals the length of the linked lisst
# Space Complexity: O(n) where n equals the length of the linked list
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Space complexity O(n)? You aren't creating any additional data structure or using recursion.

def length
return 0 if !@head
length_count = 0
current_position = @head
until current_position == nil
length_count += 1
current_position = current_position.next
end
return length_count
end

# method that returns the value at a given index in the linked list
# index count starts at 0
# returns nil if there are fewer nodes in the linked list than the index value
# Time Complexity:
# Space Complexity
def get_at_index(index)
raise NotImplementedError
# method that inserts a given value as a new last node in the linked list
# Time Complexity: O(n) where n is the length of the linked list
# Space Complexity: O(1) constant because adding one node
def add_last(value)
new_node = Node.new(value)
if @head == nil
@head = new_node
return @head
end

# method to print all the values in the linked list
# Time Complexity:
# Space Complexity
def visit
raise NotImplementedError
current = @head
until current.next == nil
current = current.next
end
current.next = new_node
end

# method to delete the first node found with specified value
# Time Complexity:
# Space Complexity
def delete(value)
raise NotImplementedError
end
# method that returns the value of the last node in the linked list
# returns nil if the linked list is empty
# Time Complexity: O(n) where n is the length of the linked list
# Space Complexity: O(1) constant because only retrieving last value
def get_last
return nil if !@head
current = @head
while current.next != nil
current = current.next
end
return current.data
end

# method to reverse the singly linked list
# note: the nodes should be moved and not just the values in the nodes
# Time Complexity:
# Space Complexity
def reverse
raise NotImplementedError
end
# method that returns the value at a given index in the linked list
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And a bunch of unimplemented methods.

# index count starts at 0
# returns nil if there are fewer nodes in the linked list than the index value
# Time Complexity:
# Space Complexity:
def get_at_index(index)
raise NotImplementedError
end

# method to find if the linked list contains a node with specified value
# returns true if found, false otherwise
# Time Complexity:
# Space Complexity
def search(value)
raise NotImplementedError
end

## Advanced Exercises
# returns the value at the middle element in the singly linked list
# Time Complexity:
# Space Complexity
def find_middle_value
raise NotImplementedError
end
# method to return the max value in the linked list
# returns the data value and not the node
# Time Complexity:
# Space Complexity
def find_max
raise NotImplementedError
end

# find the nth node from the end and return its value
# assume indexing starts at 0 while counting to n
# Time Complexity:
# Space Complexity
def find_nth_from_end(n)
raise NotImplementedError
end
# method to return the min value in the linked list
# returns the data value and not the node
# Time Complexity:
# Space Complexity
def find_min
raise NotImplementedError
end

# checks if the linked list has a cycle. A cycle exists if any node in the
# linked list links to a node already visited.
# returns true if a cycle is found, false otherwise.
# Time Complexity:
# Space Complexity
def has_cycle
raise NotImplementedError
end
# method to print all the values in the linked list
# Time Complexity:
# Space Complexity
def visit
raise NotImplementedError
end

# method to delete the first node found with specified value
# Time Complexity:
# Space Complexity
def delete(value)
raise NotImplementedError
end

# Additional Exercises
# returns the value in the first node
# returns nil if the list is empty
# Time Complexity:
# Space Complexity
def get_first
raise NotImplementedError
end
# method to reverse the singly linked list
# note: the nodes should be moved and not just the values in the nodes
# Time Complexity:
# Space Complexity
def reverse
raise NotImplementedError
end

# method that inserts a given value as a new last node in the linked list
# Time Complexity:
# Space Complexity
def add_last(value)
raise NotImplementedError
end
## Advanced Exercises
# returns the value at the middle element in the singly linked list
# Time Complexity:
# Space Complexity
def find_middle_value
raise NotImplementedError
end

# method that returns the value of the last node in the linked list
# returns nil if the linked list is empty
# Time Complexity:
# Space Complexity
def get_last
raise NotImplementedError
end
# find the nth node from the end and return its value
# assume indexing starts at 0 while counting to n
# Time Complexity:
# Space Complexity
def find_nth_from_end(n)
raise NotImplementedError
end

# method to insert a new node with specific data value, assuming the linked
# list is sorted in ascending order
# Time Complexity:
# Space Complexity
def insert_ascending(value)
raise NotImplementedError
end
# checks if the linked list has a cycle. A cycle exists if any node in the
# linked list links to a node already visited.
# returns true if a cycle is found, false otherwise.
# Time Complexity:
# Space Complexity
def has_cycle
raise NotImplementedError
end

# Helper method for tests
# Creates a cycle in the linked list for testing purposes
# Assumes the linked list has at least one node
def create_cycle
return if @head == nil # don't do anything if the linked list is empty
# method to insert a new node with specific data value, assuming the linked
# list is sorted in ascending order
# Time Complexity:
# Space Complexity
def insert_ascending(value)
raise NotImplementedError
end

# navigate to last node
current = @head
while current.next != nil
current = current.next
end
# Helper method for tests
# Creates a cycle in the linked list for testing purposes
# Assumes the linked list has at least one node
def create_cycle
return if @head == nil # don't do anything if the linked list is empty

current.next = @head # make the last node link to first node
# navigate to last node
current = @head
while current.next != nil
current = current.next
end

current.next = @head # make the last node link to first node
end
end