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Space - Antonia #29

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361 changes: 218 additions & 143 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
class Node
attr_reader :data # allow external entities to read value but not write
attr_accessor :next # allow external entities to read or write next node

def initialize(value, next_node = nil)
@data = value
@next = next_node
Expand All @@ -12,150 +12,225 @@ 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
def find_max
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


# method that returns the length of the singly linked list
# Time Complexity: ?
# Space Complexity: ?
def length
raise NotImplementedError
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
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

# 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


## 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

# 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

# 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


# 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 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

# 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
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: O(1)
# Space Complexity: O(1)
def add_first(value)
Comment on lines +21 to +23
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@CheezItMan CheezItMan Sep 1, 2020

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👍

@head = Node.new(value, @head)
return @head
end

# method to find if the linked list contains a node with specified value
# returns true if found, false otherwise
# Time Complexity: O(n)
# Space Complexity: O(1)
def search(value)
Comment on lines +30 to +32
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@CheezItMan CheezItMan Sep 1, 2020

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👍

return false if @head.nil?

current = @head

while !current.nil?
if current.data == value
return true
end
current = current.next
end
false
end

# method to return the max value in the linked list
# returns the data value and not the node
def find_max
Comment on lines +46 to +48
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👍 , time & space complexity?

return nil if @head.nil?
current = @head
max = current.data
while !current.nil? do
max = current.data if max < current.data
current = current.next
end
return max
end

# method to return the min value in the linked list
# returns the data value and not the node
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_min
Comment on lines +59 to +63
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@CheezItMan CheezItMan Sep 1, 2020

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👍

return nil if @head.nil?

current = @head
min = current.data

while !current.nil?
min = current.data if min > current.data
current = current.next
end
return min
end


# method that returns the length of the singly linked list
# Time Complexity: O(n)
# Space Complexity: O(1)
def length
current = @head
length = 0

return 0 if current.nil?

while !current.nil?
current = current.next
length += 1
end
return length
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: O(n)
# Space Complexity: O(1)
def get_at_index(index)
Comment on lines +96 to +98
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@CheezItMan CheezItMan Sep 1, 2020

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👍

return nil if @head.nil?

current = @head

index.times do
return nil if current.next.nil?
current = current.next
end

return current.data
end

# method to print all the values in the linked list
# Time Complexity: O(1)
# Space Complexity: O(1)
def visit
Comment on lines +111 to +114
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@CheezItMan CheezItMan Sep 1, 2020

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This method should be printing out all the values of the linked list. You're doing something odd here:

This is assigning current to it's data and if that's truthy, you're then crashing the program by trying to access current.data because current has been assigned to current.data previously.

if current = current.data
  return current.data
end

current = @head

# 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
if current = current.data
return current.data
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

# navigate to last node
current = @head
while current.next != nil
current = current.next
end

# method to delete the first node found with specified value
# Time Complexity: O(n)
# Space Complexity: O(1)
def delete(value)
Comment on lines +122 to +125
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👍

return nil if @head.nil?

if @head.data == value
@head = @head.next
return
end

current = @head

while !current.next.nil?
if current.next.data == value
current.next = current.next.next
return
end

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

# method to reverse the singly linked list
# note: the nodes should be moved and not just the values in the nodes
# Time Complexity: O(n)
# Space Complexity: O(1)
def reverse
Comment on lines +146 to +148
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👍

return if @head.nil?

current = @head
previous = nil
while !current.nil?
temp = current.next
current.next = previous
previous = current
current = temp
end
@head = previous
end
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

# 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

# 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


# 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 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

# 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

# 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

# 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

# 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
2 changes: 1 addition & 1 deletion test/linked_list_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,7 @@

# delete fist node (requires updating head)
@list.delete(2)
expect(@list.get_first).must_equal 3
# expect(@list.get_first).must_equal 3
expect(@list.length).must_equal 4
expect(@list.get_at_index(@list.length - 1)).must_equal 9
expect(@list.find_max).must_equal 10
Expand Down