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Ports - Ngoc #36

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e028716
updated find min max methods
lebaongoc Aug 28, 2019
3819505
added delete updated add_last functions
lebaongoc Aug 29, 2019
a39cd1a
added reverse method
lebaongoc Sep 4, 2019
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223 changes: 185 additions & 38 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -18,90 +18,213 @@ 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(n)
# Space Complexity: O(1)
def add_first(value)
raise NotImplementedError
if @head == nil
@head = Node.new(value, nil)
else
new_node = Node.new(value, nil)
new_node.next = @head
@head = new_node
end
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
if @head == nil
return false
else
current = @head
until current == nil
if current.data == value
return true
else
return false
end
end
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
if @head == nil
return nil
end
# p @head
max_val = @head.data
current = @head
until current == nil
if current.data != nil && current.data > max_val
max_val = current.data

end
current = current.next
end
return max_val

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
if @head == nil
return nil
end
min_val = @head.data
current = @head

until current == nil
if current.data != nil && current.data < min_val
min_val = current.data
end
current = current.next
end
return min_val

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
current = @head
count = 0
until current == nil
count += 1
current = current.next
end
return count
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
current = @head
count = 0
until current == nil
if count == index && current != nil
return current.data
end
count += 1
current = current.next
end
if count < index
return nil
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
p 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)
# Space Complexity: O(1)
def delete(value)
raise NotImplementedError
current = @head
if current == nil
return
end
if current.data == value
@head = current.next
return
end
until current == nil
previous_node = current
current = current.next
if current.data == value && current != nil
previous_node.next = current.next
return
end
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: O(1)
def reverse
raise NotImplementedError
current = @head
previous = nil
temp = nil
until current == nil
temp = current.next
current.next = previous
previous = current
current = temp
end
@head = previous
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
slow = @head
fast = @head.next

until fast == nil
slow = slow.next
fast = fast.next
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
# Time Complexity:
# Space Complexity
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@CheezItMan CheezItMan Oct 1, 2019

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Time and space complexity?

def find_nth_from_end(n)
raise NotImplementedError

counter = 0
current = @head
trailing_current = nil
if current == nil
return nil
end
if n > length
return nil
end

while current != nil
if counter == n + 1
trailing_current = @head
end
if trailing_current != nil
trailing_current = trailing_current.next
end
current = current.next
counter += 1
end
if counter == n + 1
return @head.data
end
if trailing_current == nil
return nil
end
return trailing_current.data
end

# checks if the linked list has a cycle. A cycle exists if any node in the
Expand All @@ -120,22 +243,46 @@ def has_cycle
# Time Complexity:
# Space Complexity
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@CheezItMan CheezItMan Oct 1, 2019

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Should be O(1) for both

def get_first
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: O(1)
def add_last(value)
raise NotImplementedError
current = @head
prev = @head
new_node = Node.new(value, nil)
if current == nil
@head = new_node
return
end
until current == nil
prev = current
current = current.next
end
prev.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)
# Space Complexity: O(1)
def get_last
raise NotImplementedError
current = @head
second_to_last_node = @head
if current == nil
return nil
end
until current == nil
prev = current
current = current.next
end
return prev.data
end

# method to insert a new node with specific data value, assuming the linked
Expand Down
5 changes: 5 additions & 0 deletions test/linked_list_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,8 @@

# Assert
expect(@list.get_first).must_equal 3
expect(@list.search(3)).must_equal true
expect(@list.search(99)).must_equal false
end

it 'will return `nil` for `getFirst` if the list is empty' do
Expand Down Expand Up @@ -140,7 +142,10 @@
expect(@list.find_min).must_equal 0
count += 1
end


@list.add_last(100)

@list.add_first(-12)

# Act-Assert
Expand Down