Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Ports - Sopheary #33

Open
wants to merge 6 commits into
base: master
Choose a base branch
from
Open

Ports - Sopheary #33

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
311bc90
getting stuck at get_at_index
Aug 29, 2019
09ef3a1
error with get-last
Aug 30, 2019
fe42a1a
all tests passed
Sep 2, 2019
33d5051
middle value
Sep 2, 2019
3353a96
insert_ascending
Sep 2, 2019
7809145
has_cycle
Sep 2, 2019
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
229 changes: 181 additions & 48 deletions lib/linked_list.rb
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,132 +18,265 @@ 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)
# Space Complexity O(1)
def add_first(value)
raise NotImplementedError
new_node = Node.new(value)
new_node.next = @head
@head = new_node
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)
# Space Complexity: O(1)
def search(value)
raise NotImplementedError
return false if @head.nil?
return true if @head.data = value
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is this needed? Wouldn't the loop catch this as well?

current = @head
until current.data.nil?
return true if current.data = value
current = current.next
end
end

# method to return the max value in the linked list
# returns the data value and not the node
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_max
raise NotImplementedError
return nil if @head.nil?
current = @head
max = current.data
until current.nil?
max = current.data if current.data > max
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:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_min
raise NotImplementedError
return nil if @head.nil?
current = @head
min = current.data
until current.nil?
if current.data < min
min = current.data
end
current = current.next
end
return min
end


# method that returns the length of the singly linked list
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def length
raise NotImplementedError
return 0 if @head.nil?
length = 0
current = @head
until 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:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def get_at_index(index)
raise NotImplementedError
return nil if length <= index
current = @head
count = 0
until current.nil?
return current.data if count == index
current = current.next
count += 1
end
end

# method to print all the values in the linked list
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def visit
raise NotImplementedError
current = @head
until current.nil?
puts current.data
current = current.next
end
end

# method to delete the first node found with specified value
# Time Complexity:
# Space Complexity
# Time Complexity: O(n) where n is the number of nodes
# Space Complexity: O(1)
def delete(value)
raise NotImplementedError
return if @head.nil?
current = @head

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

prev = current
until current.nil?
if current.data == value
prev.next = current.next
else
prev = current
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:
# Space Complexity
# Time Complexity: O(n) where n is the number of nodes
# Space Complexity: O(1)
def reverse
raise NotImplementedError
return nil if @head.nil?
prev = nil
current = @head
until current.nil?
temp = current.next
current.next = prev
prev = current
current = temp
end

@head = prev

end


## Advanced Exercises
# returns the value at the middle element in the singly linked list
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_middle_value
raise NotImplementedError
return nil if @head.nil?
current = @head
if length % 2 == 0
return nil
else
middle_index = length / 2
end
index = 0
until current.nil?
return current.data if index == middle_index
current = current.next
index += 1
end

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
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_nth_from_end(n)
raise NotImplementedError
return nil if @head.nil?
current = @head
index = 0
until current.nil?
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

What if n is larger than the length of the list?

if index == length - n - 1
return current.data
end
index += 1
current = current.next
end
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
# Time Complexity: O(n)
# Space Complexity: O(1)
def has_cycle
raise NotImplementedError
return nil if @head.nil?
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

👍

slow_p = @head
fast_p = @head
while slow_p != nil && fast_p != nil and fast_p.next != nil
slow_p = slow_p.next
fast_p = fast_p.next.next
if slow_p == fast_p
return true
end
return false
end
end


# Additional Exercises
# returns the value in the first node
# returns nil if the list is empty
# Time Complexity:
# Space Complexity
# Time Complexity: O(1)
# Space Complexity: O(1)
def get_first
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
# Time Complexity:
# Space Complexity
# Time Complexity: O(n) where n is the number of nodes
# Space Complexity: O(1)
def add_last(value)
raise NotImplementedError
new_node = Node.new(value)
if @head.nil?
@head = new_node
return
end
current = @head
until current.next.nil?
current = current.next
end
current.next = new_node

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
# Time Complexity: O(n) where n is the number of nodes
# Space Complexity: O(1)
def get_last
raise NotImplementedError
return nil if @head.nil?
current = @head
until current.next.nil?
current = current.next
end
return current.data
end

# method to insert a new node with specific data value, assuming the linked
# list is sorted in ascending order
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: O(1)
def insert_ascending(value)
raise NotImplementedError
new_node = Node.new(value)
@head = new_node if @head.nil?
current = @head
if current.data > new_node.data
temp = @head
@head = new_node
new_node.next = temp
end
until current.nil?
if current.data <= value && current.next.data > value
temp = current.next
current.next = new_node
new_node.next = temp
end
current = current.next
end
end

# Helper method for tests
Expand Down