Implement locking in a binary tree. A binary tree node can be locked or unlocked only if all of its descendants or ancestors are not locked. Design a binary tree node class with the following methods: is_locked, which returns whether the node is locked lock, which attempts to lock the node. If it cannot be locked, then it should return false. Ot…

daily-coding-problem-24.rb

class BinaryTreeLock
    attr_accessor :locked, :left, :right

    def initialize(left=nil, right=nil, unlocked)
        @left = left 
        @right = right
        @unlocked = unlocked
    end

    def lock
        if is_unlocked() && @unlocked
            @locked = true
            return true
        end 
        return false
    end 

    def unlock 
        if is_unlocked() && !@unlocked
            @locked = false
            return true
        end 
        return false
    end

    def is_unlocked
        res = true 
        if @left.nil? && @right.nil?
            return @unlocked
        end 
        if !@left.nil? 
            res &= @left.is_unlocked()
        end 
        if !@right.nil? 
            res &= @right.is_unlocked()
        end 
        return res 
    end 
end

class Assertion
    attr_accessor :root, :expected, :msg

    def initialize(root, expected, msg="")
        @root = root 
        @expected = expected
        @msg = msg 
    end
end 

def test 
    test = Array.new
    test << Assertion.new(BinaryTreeLock.new(unlocked = true), true, msg="One unlocked node")
    test << Assertion.new(BinaryTreeLock.new(unlocked = false), false, msg="One locked node")
    test << Assertion.new(BinaryTreeLock.new(left=BinaryTreeLock.new(unlocked=true), right=BinaryTreeLock.new(unlocked=true), unlocked=true), true, msg="Root with two children, all unlocked")
    test <<  Assertion.new(BinaryTreeLock.new(left=BinaryTreeLock.new(unlocked=false), right=BinaryTreeLock.new(unlocked=true), unlocked=true), false, msg="Root with two children, left is locked, right is unlocked")
    test << Assertion.new(BinaryTreeLock.new(left=BinaryTreeLock.new(unlocked=true), right=BinaryTreeLock.new(unlocked=false), unlocked=true), false, msg="Root with two children, left is unlocked, right is locked")
    test.each do |t|
        puts "#{t.msg}:\n#{t.root.is_unlocked()==t.expected()}"  
    end 
end

if __FILE__ == $0 
    test()
end