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=[]) click to toggle source

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

<<(obj)
Alias for: push
each(&block) click to toggle source

Iterate over the Stack in LIFO order.

# File lib/containers/stack.rb, line 63
def each(&block)
  @container.each_backward(&block)
end
empty?() click to toggle source

Returns true if the stack is empty, false otherwise.

# File lib/containers/stack.rb, line 58
def empty?
  @container.empty?
end
next() click to toggle source

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() click to toggle source

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) click to toggle source

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() click to toggle source

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