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Ting Wong - Linked List #20

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35c8cfa
insert ascending order
Sep 10, 2017
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completed assignment
Sep 13, 2017
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241 changes: 222 additions & 19 deletions linked_list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -19,77 +19,279 @@ 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
def insert(value)
puts "Not implemented"
newNode = Node.new(value)
if @head == nil
@head = newNode
else
newNode.next = @head
@head = newNode
end
end

# method to find if the linked list contains a node with specified value
# returns true if found, false otherwise
def search(value)
puts "Not implemented"
current = @head
if @head == nil
return false
else
while current != nil
if current == value
return true
else
current = current.next
end
end
return false
end
end

# method to return the max value in the linked list
# returns the data value and not the node
def find_max
puts "Not implemented"
current = @head
max = current.data

if @head == nil
return 0
else
while current != nil
if current.data > max
max = current.data
end
current = current.next
end
return max
end
end

# method to return the min value in the linked list
# returns the data value and not the node
def find_min
puts "Not implemented"
current = @head
min = current.data

if @head == nil
return 0
else
while current != nil
if current.data < min
min = current.data
end
current = current.next
end
return min
end
end

# method that returns the length of the singly linked list
def length
puts "Not implemented"
count = 0
current = @head

if @head == nil
return 0
else
while current != nil
count += 1
current = current.next
end
return count
end
end

# method to return the value of the nth element from the beginning
# assume indexing starts at 0 while counting to n
def find_nth_from_beginning(n)
puts "Not implemented"
current = @head
n_count = 0

if @head == nil
return 0
elsif n == 0
return @head.data
else
while current != nil
if n_count == n
return current.data
else
current = current.next
n_count += 1
end
end
end

end

# method to insert a new node with specific data value, assuming the linked
# list is sorted in ascending order
def insert_ascending(value)
puts "Not implemented"
newNode = Node.new(value)
current = @head
temp = current

if @head == nil
@head = newNode
return
end

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

while current.next != nil
if value < current.next.data
temp = current.next
current.next = newNode
newNode.next = temp
return
else
current = current.next
end
end

current.next = newNode
newNode.next = nil

end

# method to print all the values in the linked list
def visit
puts "Not implemented"
current = @head
if @head == nil
return 0
else
while current != nil
print current.data
current = current.next
end
end
end

# method to delete the first node found with specified value
def delete(value)
puts "Not implemented"
current = @head

if @head == nil
return 0
elsif @head.data == value
@head = current.next
else
while current.next != nil
if current.next.data == value
current.next = current.next.next
return
else
current = current.next
end
end
end

end

# method to reverse the singly linked list
# note: the nodes should be moved and not just the values in the nodes
def reverse
puts "Not implemented"
current = @head
previous = nil
temp = current.next

if @head == nil
return 0
else
while current != nil
temp = current.next
current.next = previous
previous = current
current = temp
end
end

@head = previous

end


## Advanced Exercises
# returns the value at the middle element in the singly linked list
def find_middle_value
puts "Not implemented"
fast = @head.next
slow = @head

if @head == nil
return 0
elsif @head.next == nil
return @head
end

while fast != nil
fast = fast.next
slow = slow.next
if fast != nil
fast = fast.next
end
end

return slow.data
end

# find the nth node from the end and return its value
# assume indexing starts at 0 while counting to n
def find_nth_from_end(n)
puts "Not implemented"
current = @head
counter = 0
trailingPointer = @head

if @head == nil
return 0
end

until current.next == nil
current = current.next
counter += 1
if counter > n
trailingPointer = trailingPointer.next
end
end
return trailingPointer.data

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.
def has_cycle
puts "Not implemented"
fastPointer = @head
slowPointer = @head

if @head == nil
return 0
end

if @head.next == nil
return false
end

while fastPointer != nil
fastPointer = fastPointer.next
slowPointer = slowPointer.next

if fastPointer != nil
fastPointer = fastPointer.next
else
return false
end

if fastPointer == slowPointer
return true
end
end

return false


end

# Creates a cycle in the linked list for testing purposes
Expand All @@ -112,25 +314,25 @@ def create_cycle
# Create an object of linked list class
my_linked_list = LinkedList.new()

# Add some values to the linked list
# # Add some values to the linked list
puts "Adding 5, 3 and 1 to the linked list."
my_linked_list.insert(5)
my_linked_list.insert(3)
my_linked_list.insert(1)

# print all elements
#
# # print all elements
puts "Printing elements in the linked list:"
my_linked_list.visit

# Find the value at the nth node
puts "Confirming values in the linked list using find_nth_from_beginning method."
puts "\nConfirming values in the linked list using find_nth_from_beginning method."
value = my_linked_list.find_nth_from_beginning(2)
puts "BUG: Value at index 2 should be 5 and is #{value}" if value != 5
value = my_linked_list.find_nth_from_beginning(1)
puts "BUG: Value at index 1 should be 3 and is #{value}" if value != 3
value = my_linked_list.find_nth_from_beginning(0)
puts "BUG: Value at index 0 should be 1 and is #{value}" if value != 1

#
# print all elements
puts "Printing elements in the linked list:"
my_linked_list.visit
Expand Down Expand Up @@ -161,11 +363,12 @@ def create_cycle
puts "BUG: Length should be 5 and not #{my_linked_list_length}" if my_linked_list_length != 5

# find min and max
puts "\n"
puts "Confirming min and max values in the linked list."
min = my_linked_list.find_min
puts "BUG: Min value should be 1 and not #{min}" if min != 1
max = my_linked_list.find_max
puts "BUG: Max value should be 5 and not #{max}" if max != 6
puts "BUG: Max value should be 6 and not #{max}" if max != 6

# delete value
puts "Deleting node with value 5 from the linked list."
Expand Down