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Earth - Kal #36

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1c6de75
methods finished, all tests passing
kashenafi May 24, 2021
8d733f5
added s & t complexity
kashenafi Jun 3, 2021
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122 changes: 101 additions & 21 deletions lib/tree.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,12 @@ class TreeNode
attr_reader :key, :value
attr_accessor :left, :right

def initialize(key, val)
def initialize(key, val)
@key = key
@value = val
@left = nil
@right = nil
end
end
end

class Tree
Expand All @@ -16,47 +16,127 @@ def initialize
@root = nil
end

# Time Complexity:
# Space Complexity:
def add(key, value)
raise NotImplementedError
# Time Complexity: O(log n) if balanced, otherwise O(n) where n is number of nodes
# Space Complexity: O(n), n is height
def add(key, value=nil)
Comment on lines +19 to +21
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@CheezItMan CheezItMan Jun 11, 2021

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👍 Yeah recursion! You threw me with the O(n) space complexity until I saw the note on height.

new_node = TreeNode.new(key, value)

if @root.nil?
@root = new_node
else
add_helper(@root, new_node)
end
end

# Time Complexity:
# Space Complexity:
def add_helper(curr_node, new_node)
return new_node if curr_node.nil?

if new_node.key <= curr_node.key
curr_node.left = add_helper(curr_node.left, new_node)
else
curr_node.right = add_helper(curr_node.right, new_node)
end

return curr_node
end

# Time Complexity: O(log n) if balanced
# Space Complexity: O(n)
def find(key)
Comment on lines +43 to 45
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@CheezItMan CheezItMan Jun 11, 2021

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👍 I assume space complexity is related to the height.

raise NotImplementedError
find_helper(@root, key) #starts at root
end

# Time Complexity:
# Space Complexity:
def find_helper(current, key)
return if current.nil?
if key == current.key
return current.value
elsif key < current.key
find_helper(current.left, key)
else
find_helper(current.right, key)
end
end

# Time Complexity: O(n), n is number of nodes
# Space Complexity: O(n)
def inorder
Comment on lines +60 to 62
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@CheezItMan CheezItMan Jun 11, 2021

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👍

raise NotImplementedError
return inorder_helper(@root, [])
end

def inorder_helper(current, list)
return list if current.nil?
inorder_helper(current.left, list)
list << {key: current.key, value: current.value}
inorder_helper(current.right, list)
return list
end

# Time Complexity:
# Space Complexity:
# Time Complexity: O(n)
# Space Complexity: O(n)
def preorder
Comment on lines +74 to 76
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@CheezItMan CheezItMan Jun 11, 2021

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👍

raise NotImplementedError
return preorder_helper(@root, [])
end

# Time Complexity:
# Space Complexity:
def preorder_helper(current, list)
return list if current.nil?
list << {key: current.key, value: current.value}
preorder_helper(current.left, list)
preorder_helper(current.right, list)
end

# Time Complexity: O(n)
# Space Complexity: O(n)
def postorder
Comment on lines +87 to 89
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@CheezItMan CheezItMan Jun 11, 2021

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👍

raise NotImplementedError
return postorder_helper(@root, [])
end

def postorder_helper(current, list)
return list if current.nil?
postorder_helper(current.left, list)
postorder_helper(current.right, list)
list << {key: current.key, value: current.value}
end

# Time Complexity:
# Space Complexity:
def height
raise NotImplementedError
def height(current = @root)
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@CheezItMan CheezItMan Jun 11, 2021

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👍 Time/space complexity?

return 0 if current.nil?
return 1 if current.right.nil? && current.left.nil?

left_count = 0
right_count = 0
left_count += 1 + height(current.left)
right_count += 1 + height(current.right)
left_count > right_count ? left_count : right_count
end

def height_helper(node, side, count)
return count if node.nil?

count += 1
if side == 'left'
height_helper(node.left, 'left', count)
else
height_helper(node.right, 'right', count)
end
end

# Optional Method
# Time Complexity:
# Space Complexity:
def bfs
Comment on lines 125 to 127
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@CheezItMan CheezItMan Jun 11, 2021

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Yeah BFS!

Time/space complexity

raise NotImplementedError
return [] if @root.nil?
queue = []
list = []
queue.push(@root)
while queue.length > 0
current = queue[0]
list << {key: current.key, value: current.value}
queue.push(current.left) if current.left
queue.push(current.right) if current.right
queue.shift
end
return list
end

# Useful for printing
Expand Down