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Fire - Roshni #18

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173 changes: 138 additions & 35 deletions lib/linked_list.rb
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@

# Defines a node in the singly linked list
class Node
attr_reader :data # allow external entities to read value but not write
Expand All @@ -18,95 +17,199 @@ 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)
Comment on lines +20 to 22
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@CheezItMan CheezItMan Mar 23, 2021

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raise NotImplementedError
if @head
new_node = Node.new(value)
new_node.next = @head
@head = new_node
else
@head = Node.new(value)
end
Comment on lines +23 to +29
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Let me suggest this as simpler.

Suggested change
if @head
new_node = Node.new(value)
new_node.next = @head
@head = new_node
else
@head = Node.new(value)
end
@head = Node.new(value, @head)

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)
Comment on lines +34 to 36
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raise NotImplementedError
return false if @head.nil?

current = @head
while current
if current.data == value
return true
else
current = current.next
end
end
return false
end

# method to return the max value in the linked list
# returns the data value and not the node
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_max
Comment on lines +52 to 54
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raise NotImplementedError
return nil if @head.nil?
current = @head
max = current.data

until current.nil?
if current.data > max
max = current.data
end
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
Comment on lines +71 to 73
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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


# 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
Comment on lines +91 to 93
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raise NotImplementedError
return @head ? @head.data : nil
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)
Comment on lines +98 to 100
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raise NotImplementedError
if @head
current = @head
until current.next.nil?
current = current.next
end
current.next = Node.new(value)
else
@head = Node.new(value)
end
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
Comment on lines +113 to 115
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raise NotImplementedError
length = 0
current = @head

while current
length += 1
current = current.next
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)
Comment on lines +129 to 131
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raise NotImplementedError
return nil if self.length < index || @head.nil?
i = 0
current = @head

while current
if i == index
return current.data
else
current = current.next
i += 1
end
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
Comment on lines +147 to 149
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raise NotImplementedError
return nil if @head.nil?

current = @head
while current
print 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)
Comment on lines +160 to 162
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raise NotImplementedError
return nil if @head.nil?

if @head.data == value
@head = @head.next
return
else
current = @head
while current.next
if current.next.data == value
current.next = current.next.next
return
end
current = current.next
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
Comment on lines +182 to 184
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raise NotImplementedError
return nil if @head.nil?

current = @head
prev = nil

while current
temp = current.next
current.next = prev
prev = current
current = temp
end
@head = prev
return @head
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
Comment on lines +202 to 204
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raise NotImplementedError
return nil if @head.nil?

current = @head
until current.next.nil?
current = current.next
end

return current.data
end

## Advanced Exercises
Expand Down
2 changes: 1 addition & 1 deletion test/linked_list_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@
end
end

xdescribe "Optional addLast & getLast" do
describe "Optional addLast & getLast" do
it "will add to the front if the list is empty" do
@list.add_last(1)
expect(@list.get_at_index(0)).must_equal 1
Expand Down