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Maria-W #35

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224 changes: 185 additions & 39 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -18,73 +18,178 @@ 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: constant
# Space Complexity constant
def add_first(value)
raise NotImplementedError
new_node = Node.new(value)
if @head != nil
new_node.next = @head
end

@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 constant
def search(value)
raise NotImplementedError
if @head == nil
return false
end

current = @head
while @next != nil
if current.next == value
return true
end
end
return false
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: constant
def find_max
raise NotImplementedError
return nil if @head == nil

max_value = current.data
current = @head

while current.next != nil
if current.data > max_value
max_value = current.data
end
current = current.next
end

if current.data > max_value
max_value = current.data
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)
# Space Complexity: constant
def find_min
raise NotImplementedError
#raise NotImplementedError
return nil if @head == nil
min_value = @head.data
current = @head

while current.next != nil
if current.data < min_value
min_value = current.data
end
current = current.next
end

if current.data < min_value
min_value = current.data
end
return min_value

end


# method that returns the length of the singly linked list
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: constant
def length
raise NotImplementedError
#raise NotImplementedError
count = 0

return count if @head == nil

current = @head

while current.next != nil
count += 1
current = current.next
end

return count + 1
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: comstamt
def get_at_index(index)
raise NotImplementedError
#raise NotImplementedError
return nil if @head == nil

current = @head
count = 0

until count == index
return nil if current.next == nil
current = current.next
count += 1
end
return current.data
end

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

puts current.data

end

# method to delete the first node found with specified value
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: constant
def delete(value)
raise NotImplementedError
#raise NotImplementedError
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 = 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)
# Space Complexity: constant
def reverse
raise NotImplementedError
#raise NotImplementedError
current = @head
previous_node = nil

while current != nil
nextNode = current.next
current.next = previous_node
previous_node = current
current = nextNode
end
@head = previous_node
end


Expand All @@ -94,21 +199,39 @@ def reverse
# 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
#raise NotImplementedError
current = @head
index = 0

while current != nil && index != n
current = current.next
index += 1

if current == nil
return nil
end

new_current = @head
while current.next != nil
current = current.next
new_current = new_current.next
end
return new_current.data
end
Comment on lines 209 to 228
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A couple of things:

  1. Your indentation is off here.
  2. You are missing an end
  3. Even beyond that, it's not working because on empty lists or lists shorter than what's given new_current may end up being nil.


# 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:
# Space Complexity:
def has_cycle
raise NotImplementedError
end
Expand All @@ -117,25 +240,48 @@ def has_cycle
# Additional Exercises
# returns the value in the first node
# returns nil if the list is empty
# Time Complexity:
# Space Complexity
# Time Complexity: Constant
# Space Complexity: constant
def get_first
raise NotImplementedError
#raise NotImplementedError
if @head == nil
return nil
else
return @head.data
end

end

# method that inserts a given value as a new last node in the linked list
# Time Complexity:
# Space Complexity
# Time Complexity: O(n)
# Space Complexity: constant
def add_last(value)
raise NotImplementedError
#raise NotImplementedError
new_node = Node.new(value)

if @head == nil
@head = new_node
else
current = @head
while current.next != nil
current = current.next
end
current.next = new_node
end
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)
# Space Complexity: constant
def get_last
raise NotImplementedError
#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
Expand Down