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Space - Jessica #24

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171 changes: 143 additions & 28 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,12 @@
# Defines a node in the singly linked list
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
attr_accessor :next, :previous, :data # allow external entities to read or write next node

def initialize(value, next_node = nil)
def initialize(value, next_node = nil, prev_node = nil)
@data = value
@next = next_node
@previous = prev_node
end
end

Expand All @@ -18,71 +19,184 @@ def initialize

# 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: ?
# Time Complexity: O(1), since it will always have direct access to the front of the list
# Space Complexity: O(1)
def add_first(value)
Comment on lines +22 to 24
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raise NotImplementedError
if @head == nil
newNode = Node.new(value)
@head = newNode
return
end

current_head = @head
newNode = Node.new(value, next_node = current_head)
current_head.previous = newNode
@head = newNode
return
end

# method to find if the linked list contains a node with specified value
# returns true if found, false otherwise
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n), n being up to the length of the linked list
# Space Complexity: O(1)
def search(value)
Comment on lines +40 to 42
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raise NotImplementedError
return false if @head == nil
return true if @head.data == value

current_node = @head
until current_node == nil
if current_node.data == value
return true
else
current_node = current_node.next
end
end

return false
end

# method to return the max value in the linked list
# returns the data value and not the node
# Time Complexity: O(n), n being up to the length of the linked list
# Space Complexity: O(1)
def find_max
Comment on lines +60 to 62
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raise NotImplementedError
return nil if @head == nil

current_node = @head
max_value = current_node.data
until current_node == nil
if current_node.data > max_value
max_value = current_node.data
end
current_node = current_node.next
end

return max_value
end

# method to return the min value in the linked list
# returns the data value and not the node
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n), n being up to the length of the linked list
# Space Complexity: O(1)
def find_min
Comment on lines +79 to 81
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raise NotImplementedError
return nil if @head == nil

current_node = @head
min_value = current_node.data
until current_node == nil
if current_node.data < min_value
min_value = current_node.data
end
current_node = current_node.next
end

return min_value
end


# method that returns the length of the singly linked list
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n), n being the length of the linked list
# Space Complexity: O(1)
def length
Comment on lines +98 to 100
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raise NotImplementedError
return 0 if @head == nil

current_node = @head
length = 0
until current_node == nil
length += 1
current_node = current_node.next
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: ?
# Space Complexity: ?
# Time Complexity: O(n), n being the index to get the value at
# Space Complexity: O(1)
def get_at_index(index)
Comment on lines +116 to 118
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raise NotImplementedError
return nil if @head == nil

current_node = @head
current_index = 0
until current_node == nil
if current_index == index
return current_node.data
end
current_index += 1
current_node = current_node.next
end

return nil
end

# method to print all the values in the linked list
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n), n being the amount of nodes
# Space Complexity: O(1)
def visit
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⚠ it's not printing anything.

raise NotImplementedError
return nil if @head == nil

current_node = @head
until current_node == nil
current_node = current_node.next
end
end

# method to delete the first node found with specified value
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n), n being up to the the amount of nodes in the list
# Space Complexity: O(1)
def delete(value)
Comment on lines +147 to 149
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This is a little overly complicated, but it works.

raise NotImplementedError
return nil if @head == nil

current_node = @head
previous_node = nil
next_node = current_node.next
until current_node == nil
if current_node.data == value
# if first node is being deleted
if previous_node == nil
next_node.previous = nil
@head = next_node
return
end

# if last node is deleted
if next_node == nil
previous_node.next = nil
return
end

next_node.previous = previous_node
previous_node.next = next_node
return
end
current_node = current_node.next
next_node = current_node.next
previous_node = current_node.previous
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: ?
# Space Complexity: ?
# Time Complexity: O(n), n being the number of nodes in the list
# Space Complexity: O(1)
def reverse
Comment on lines +182 to 184
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raise NotImplementedError
return if @head == nil

length = self.length
current_node = @head

until length == 0
next_node = current_node.next
current_node.next = current_node.previous
current_node.previous = next_node
current_node = next_node if next_node != nil
length -= 1
if next_node == nil
@head = current_node
end
end
end


Expand Down Expand Up @@ -118,7 +232,8 @@ def has_cycle
# Time Complexity: ?
# Space Complexity: ?
def get_first
Comment on lines 232 to 234
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raise NotImplementedError
return nil if @head == nil
return @head.data
end

# method that inserts a given value as a new last node in the linked list
Expand Down