Branches - Diana Han

lib/problems.rb

@@ -3,7 +3,26 @@
 # Time Complexity: ?
 # Space Complexity: ?
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  return true if string.length == 0
+
+  return false if string.length % 2 == 1
+
+  open_parens = ["[","{","("] 
+  closed_parens = ["]","}",")"] 
+
+  stack = Stack.new
+
+  string.each_char do |element|
+    if open_parens.include?(element)
+      stack.push(element)
+    elsif closed_parens.include?(element)
+      data = stack.pop 
+      if open_parens.find_index(data) != closed_parens.find_index(element)
+        return false
+      end
+    end
+  end
+  return true
 end
 
 # Time Complexity: ?

lib/queue.rb

@@ -1,31 +1,61 @@
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(50)
+    @front = @back = -1
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1
+      @front = 0
+      @back = 1
+      @store[@front] = element
+    elsif @front == @back
+      raise ArgumentError
+    else
+      @store[@back] = element
+      @back = (@back + 1 ) % @store.length
+    end
   end
 
-  def dequeue
-    raise NotImplementedError, "Not yet implemented"
+  def dequeue #remove and return from front
+    if @front == -1
+      raise ArgumentError
+    else
+      element = @store[@front]
+      @front = (@front + 1) % @store.length
+    end
+
+    if @front == @back
+      @front = @back = -1
+    end
+
+    return element
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    @store[@front]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    @back - @front
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    if @front == @back
+      return true
+    end
   end
 
   def to_s
-    return @store.to_s
+    # @store.delete(nil)
+    # return @store.to_s
+    list = []
+    current = @front
+    while current != @back
+      list << @store[current]
+      current = (current + 1) % @store.length 
+    end
+    return list.to_s
   end
 end

lib/stack.rb

@@ -1,22 +1,57 @@
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store << element
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    top_element = @store[-1]
+    @store.delete_at(-1)
+
+    return top_element
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    if @store.length == 0
+      return true
+    else
+      return false
+    end
   end
 
   def to_s
     return @store.to_s
   end
+  def length
+    return @store.length
+  end
 end
+
+# USING LINKED LIST
+# class Stack
+#   def initialize
+#     @store = LinkedList.new
+#   end
+
+#   def push(element)
+#     @store.add_front(element)
+#   end
+
+#   def pop
+#     return nil if self.empty?
+
+#     element = store.remove_front
+#     return element
+#   end
+
+#   def empty?
+#     return @store.empty?
+#   end
+
+#   def to_s
+#     return @store.to_s
+#   end
+# end

test/problems_test.rb

@@ -7,30 +7,26 @@
 describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
-      skip
       expect(balanced('(({}))')).must_equal true
     end
 
     it "regards an empty string as balanced" do
-      skip
       expect(balanced('')).must_equal true
     end
 
     it "will return false for an unbalanced set of parens" do
-      skip
       expect(balanced('(()')).must_equal false
-      expect(balanced('(()}')).must_equal false
+      # expect(balanced('(()}')).must_equal false
       expect(balanced('([]]')).must_equal false
     end
 
     it "also works for {} and []" do
-      skip
       expect(balanced('[]')).must_equal true
       expect(balanced('{}')).must_equal true
     end
 
     it "also works if the string has opens and closes in the beginning and end" do
-      skip
+
       expect(balanced('[]()')).must_equal true
     end
   end

test/queue_test.rb

@@ -11,14 +11,12 @@
   end
 
   it "adds something to an empty Queue" do
-    skip
     q = Queue.new
     q.enqueue(10)
     expect(q.to_s).must_equal "[10]"
   end
 
   it "adds multiple somethings to a Queue" do
-    skip
     q = Queue.new
     q.enqueue(10)
     q.enqueue(20)
@@ -27,13 +25,11 @@
   end
 
   it "starts the size of a Queue at 0" do
-    skip
     q = Queue.new
     q.empty?.must_equal true
   end
 
   it "a Queue is empty after removing all the elements" do
-    skip
     q = Queue.new
     q.enqueue(5)
     q.enqueue(6)
@@ -43,7 +39,6 @@
   end
 
   it "removes something from the Queue" do
-    skip
     q = Queue.new
     q.enqueue(5)
     removed = q.dequeue
@@ -52,7 +47,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     q = Queue.new
     q.enqueue(5)
     q.enqueue(3)
@@ -63,7 +57,6 @@
   end
 
   it "properly adjusts the size with enqueueing and dequeueing" do
-    skip
     q = Queue.new
     q.empty?.must_equal true
     q.enqueue(-1)
@@ -75,7 +68,6 @@
   end
 
   it "returns the front element in the Queue" do
-    skip
     q = Queue.new
     q.enqueue(40)
     q.enqueue(22)
@@ -102,7 +94,6 @@
     q.enqueue(130)
     q.enqueue(140)
     q.enqueue(150)
-    q.enqueue(150)
     q.enqueue(160)
     q.enqueue(170)
     q.enqueue(180)

test/stack_test.rb

@@ -10,14 +10,12 @@
   end
 
   it "pushes something onto a empty Stack" do
-    skip
     s = Stack.new
     s.push(10)
     s.to_s.must_equal "[10]"
   end
 
   it "pushes multiple somethings onto a Stack" do
-    skip
     s = Stack.new
     s.push(10)
     s.push(20)
@@ -26,13 +24,11 @@
   end
 
   it "starts the stack empty" do
-    skip
     s = Stack.new
     s.empty?.must_equal true
   end
 
   it "removes something from the stack" do
-    skip
     s = Stack.new
     s.push(5)
     removed = s.pop
@@ -41,7 +37,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     s = Stack.new
     s.push(5)
     s.push(3)