FIRE - Tram

lib/problems.rb

@@ -1,13 +1,35 @@
 require_relative './stack.rb'
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n) - has to iterate through each char in the string input
+# Space Complexity: O(n) - the stack is directly correlated with the string.length
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  return true if string.empty?
+
+  parens_hash = {"{" => "}",
+    "[" => "]",
+    "(" => ")"
+  }
+
+  stack = Stack.new
+
+  string.each_char do |char|
+    # check if it's an open paren 
+    if parens_hash.include?(char)
+      stack.push(parens_hash[char])
+    else # it's a closed paren
+      paren = stack.pop
+      return false if char != paren
+    end
+  end
+
+  return stack.empty?
 end
 
 # Time Complexity: ?
 # Space Complexity: ?
 def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
+  stack = Stack.new
+
+
+
 end

lib/queue.rb

@@ -1,31 +1,76 @@
 class Queue
-
+  MAX_BUFFER = 20 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(MAX_BUFFER)
+    @front = -1
+    @rear = -1
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    # check if queue if full 
+    if @front == 0 && @rear == MAX_BUFFER - 1
+      raise ArgumentError, "Queue is full, sorry"
+    elsif @front == -1 # queue is empty 
+      @front = @rear = 0 
+      @store[@rear] = element
+    elsif (@rear == MAX_BUFFER - 1 && @front != 0 ) # rear need to wrap
+      @rear = 0 
+      @store[@rear] = element
+    else
+      @rear = @rear + 1
+      @store[@rear] = element
+    end
+
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+
+    raise ArgumentError, "Queue is empty" if @front == -1
+
+    data = @store[@front]
+    # @store[@front] = nil
+
+    # if the queue is now empty
+    if @front == @rear 
+      @front = @rear = -1
+    elsif @front + 1 == MAX_BUFFER # front needs to wrap around
+      @front = 0 
+    else
+      @front = @front + 1
+    end
+
+    return data
+
+
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[@front]
   end
 
+  # TODO: look at this again
   def size
-    raise NotImplementedError, "Not yet implemented"
+    return @store.length
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @front == -1
   end
 
   def to_s
-    return @store.to_s
+    # return @store.to_s
+
+    return "[]" if empty?
+    arr = []
+    current = @front 
+
+    until current == @rear
+      arr << @store[cur]
+      current = (current + 1) % MAX_BUFFER
+    end
+
+    arr << @store[current]
+
+    return arr.to_s
   end
 end

lib/stack.rb

@@ -1,19 +1,20 @@
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    return @store.add_first(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    return nil if self.empty?
+
+    return @store.remove_first
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    @store.empty?
   end
 
   def to_s

test/problems_test.rb

@@ -2,7 +2,7 @@
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
-xdescribe "Test wave 3 problems" do
+describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
 

test/test_helper.rb

@@ -10,4 +10,4 @@
 require_relative "../lib/queue.rb"
 require_relative "../lib/stack.rb"
 # Extra exercises
-# require_relative "../lib/problems.rb"
+require_relative "../lib/problems.rb"