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List implementations #3

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39 changes: 35 additions & 4 deletions array-list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -2,25 +2,56 @@

class ArrayList
def initialize
@storage = []
@storage = [nil,nil,nil,nil,nil]
@size = 0
end

def add(value)
@storage[@size] = value
@size += 1
end

def delete(value)
def delete
return nil if empty?

@size -= 1
end

def display
@size.times do |i|
puts @storage[i]
end
end

def include?(key)
@size.times do |i|
if @storage[i] == key
return true
end
end

false
end

def size
@size
end

def max
return nil if empty?

biggest = @storage[0]
@size.times do |i|
if @storage[i] > @storage[biggest]
biggest = i
end
end

@storage[biggest]
end

def empty?
@size == 0
end

end
Expand All @@ -36,6 +67,6 @@ def max
puts "Displaying Array List:"
arr.display

puts "Delete 10 and then display the array list:"
arr.delete(10)
puts "Delete last element and then display the array list:"
arr.delete
arr.display
178 changes: 115 additions & 63 deletions linked-list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -3,73 +3,101 @@
# LinkedList -> This class holds the linked list functions - adding a node, traversing and displaying the linked list

class Node
attr_accessor :value, :next_node
attr_accessor :value, :next_node

def initialize(val,next_in_line=null)
@value = val
@next_nodex = next_in_line
puts "Initialized a Node with value: " + value.to_s
end
def initialize(val,next_in_line=nil)
@value = val
@next_node = next_in_line
puts "Initialized a Node with value: " + value.to_s
end
end

class LinkedList
def initialize(val)
# Initialize a new node at the head
@head = Node.new(val,nil)
end

def add(value)
# Traverse to the end of the list
# And insert a new node over there with the specified value
current = @head
while current.next_node != nil
current = current.next_node
end
current.next_node = Node.new(value,nil)
self
end

def delete(val)
current = @head
if current.value == val
# If the head is the element to be delete, the head needs to be updated
@head = @head.next_node
else
# ... x -> y -> z
# Suppose y is the value to be deleted, you need to reshape the above list to :
# ... x->z
# ( and z is basically y.next_node )
current = @head
while (current != nil) && (current.next_node != nil) && ((current.next_node).value != val)
current = current.next_node
end

if (current != nil) && (current.next_node != nil)
current.next_node = (current.next_node).next_node
end
end
end

def display
# Traverse through the list till you hit the "nil" at the end
current = @head
full_list = []
while current.next_node != nil
full_list += [current.value.to_s]
current = current.next_node
end
full_list += [current.value.to_s]
puts full_list.join("->")
end

def include?(key)
end

def size
end

def max
end
def initialize(val)
# Initialize a new node at the head
@head = Node.new(val,nil)
end

def add(value)
# Traverse to the end of the list
# And insert a new node over there with the specified value
current = @head
while current.next_node != nil
current = current.next_node
end
current.next_node = Node.new(value,nil)
self
end

def delete(val)
current = @head
if current.value == val
# If the head is the element to be delete, the head needs to be updated
@head = @head.next_node
else
# ... x -> y -> z
# Suppose y is the value to be deleted, you need to reshape the above list to :
# ... x->z
# ( and z is basically y.next_node )
current = @head
while (current != nil) && (current.next_node != nil) && ((current.next_node).value != val)
current = current.next_node
end

if (current != nil) && (current.next_node != nil)
current.next_node = (current.next_node).next_node
end
end
end

def display
# Traverse through the list till you hit the "nil" at the end
current = @head
full_list = []
while current.next_node != nil
full_list += [current.value.to_s]
current = current.next_node
end
full_list += [current.value.to_s]
puts full_list.join("->")
end

# HOMEWORK: next 3 methods
def include?(key)
current = @head
while current.next_node != nil
return true if current.value == key
current = current.next_node
end

return true if current.value == key

false
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@sudocrystal sudocrystal May 27, 2016

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I think non-Ruby-ers will find this strange. I think you should explicitly say return false even if in Ruby this works.

end

def size
current = @head
list_size = 0
while current.next_node != nil
list_size += 1
current = current.next_node
end

list_size += 1
end
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@sudocrystal sudocrystal May 27, 2016

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This looks great and works, but in all of these (include?, size, and max) you had to account for that last node separately -- if you change your loop to while current != nil instead of while current.next_node != nil then you wouldn't need that! I told you to model after display which does it the latter way -- because sometimes you need to do something different with the last case and I wanted that to be the pattern I showed -- but now I want to point out how we could have optimized the pattern just slightly. Hopefully that makes sense!


# optional
def max
current = @head
max = 0
while current.next_node != nil
max = current.value if current.value > max
current = current.next_node
end

max = current.value if current.value > max
max
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@sudocrystal sudocrystal May 27, 2016

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ditto here

end

end

Expand All @@ -88,6 +116,23 @@ def max
ll.delete(10)
ll.display

print "Checking if 5 is included in the linked list: "
puts ll.include?(5)

print "Checking if 10 is included in the linked list: "
puts ll.include?(10)

print "Checking the size of the linked list: "
puts ll.size

ll.add(12)
puts "New size: #{ll.size}"

ll.display

print "Max value of any node is: "
puts ll.max

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@sudocrystal sudocrystal May 27, 2016

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yaya for adding more tests!

=begin
Output:
Initialized a Node with value: 5
Expand All @@ -97,4 +142,11 @@ def max
5->10->20
Delete 10 and then display the linked list:
5->20
Checking if 5 is included in the linked list: true
Checking if 10 is included in the linked list: false
Checking the size of the linked list: 2
Initialized a Node with value: 12
New size: 3
5->20->12
Max value of any node is: 20
=end