class Containers::Stack
A Stack is a container that keeps elements in a last-in first-out (LIFO) order. There are many uses for stacks, including prefix-infix-postfix conversion and backtracking problems.
This implementation uses a doubly-linked list, guaranteeing O(1) complexity for all operations.
Public Class Methods
new(ary=[])
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Create a new stack. Takes an optional array argument to initialize the stack.
s = Containers::Stack.new([1, 2, 3]) s.pop #=> 3 s.pop #=> 2
# File lib/containers/stack.rb, line 16 def initialize(ary=[]) @container = Containers::Deque.new(ary) end
Public Instance Methods
each(&block)
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Iterate over the Stack in LIFO order.
# File lib/containers/stack.rb, line 63 def each(&block) @container.each_backward(&block) end
empty?()
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Returns true if the stack is empty, false otherwise.
# File lib/containers/stack.rb, line 58 def empty? @container.empty? end
next()
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Returns the next item from the stack but does not remove it.
s = Containers::Stack.new([1, 2, 3]) s.next #=> 3 s.size #=> 3
# File lib/containers/stack.rb, line 25 def next @container.back end
pop()
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Removes the next item from the stack and returns it.
s = Containers::Stack.new([1, 2, 3]) s.pop #=> 3 s.size #=> 2
# File lib/containers/stack.rb, line 45 def pop @container.pop_back end
push(obj)
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Adds an item to the stack.
s = Containers::Stack.new([1]) s.push(2) s.pop #=> 2 s.pop #=> 1
# File lib/containers/stack.rb, line 35 def push(obj) @container.push_back(obj) end
Also aliased as: <<
size()
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Return the number of items in the stack.
s = Containers::Stack.new([1, 2, 3]) s.size #=> 3
# File lib/containers/stack.rb, line 53 def size @container.size end