Shubha 🌵

lib/problems.rb

@@ -1,9 +1,41 @@
 require_relative './stack.rb'
 
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  pairs = {
+    '}' => '{',
+    ']' => '[',
+    ')' => '('
+  }
+  stack = Stack.new
+  string.split("").each do |char|
+    if !pairs[char]
+      stack.push(char)
+    else
+      return false if pairs[char] != stack.pop()
+    end
+  end
+  stack.empty? ? (return true) : (return false)
 end
 
 def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
+  stack = Stack.new
+  postfix_expression.split("").each do |char|
+    if char == char.to_i.to_s
+      stack.push(char.to_i)
+    else
+      num1 = stack.pop()
+      num2 = stack.pop()
+      case(char)
+      when "+"
+        stack.push(num2 + num1)
+      when "-"
+        stack.push(num2 - num1)
+      when "/"
+        stack.push(num2 / num1)
+      when "*"
+        stack.push(num2 * num1)
+      end
+    end
+  end
+  return stack.pop()
 end

lib/queue.rb

@@ -1,31 +1,49 @@
 class Queue
 
-  def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+  class BufferFullError < StandardError; end
+
+  def initialize(capacity=10)
+    @capacity = capacity
+    @store = Array.new(capacity)
+    @head = @tail = 0
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    raise BufferFullError if (@tail == @head && !empty?) 
+    @store[@tail] = element
+    @tail = (@tail + 1) % @capacity
+
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    return if !@head
+    value = @store[@head]
+    @store[@head] = nil 
+    @head = (@head + 1) % @capacity
+    return value
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[@head]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    if (@head == @tail && !empty?)
+      return @capacity 
+    elsif @head == @tail
+      return 0
+    elsif @tail > @head
+      return @tail - @head
+    elsif @tail < @head
+      return @capacity - (@head - @tail)
+    end
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    @store[@head] ? (return false) : (return true)
   end
 
   def to_s
-    return @store.to_s
+    return @store.select{|value| value}.to_s
   end
 end

lib/stack.rb

@@ -1,19 +1,20 @@
+require_relative "./linked_list.rb"
+
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_last(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    @store.remove_last()
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @store.empty?
   end
 
   def to_s

test/problems_test.rb

@@ -7,40 +7,34 @@
 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
     end
 
     it "also works for {} and []" do
-      skip
       expect(balanced('[]')).must_equal true
       expect(balanced('{}')).must_equal true
     end
   end
 
   describe "postfix" do
     it "can add a 2 numbers together" do
-      skip
       expect(evaluate_postfix("34+")).must_equal 7
       expect(evaluate_postfix("34*")).must_equal 12
       expect(evaluate_postfix("34-")).must_equal -1
       expect(evaluate_postfix("34/")).must_equal 0
     end
 
     it "can add a evaluate a more complicated expression" do
-      skip
       expect(evaluate_postfix("34+2*")).must_equal 14
       expect(evaluate_postfix("34*2/")).must_equal 6
       expect(evaluate_postfix("34-1+")).must_equal 0

test/queue_test.rb

@@ -11,14 +11,12 @@
   end
 
   it "adds something to an empty Queue" do
-    skip
     q = Queue.new
     q.enqueue(10)
     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 "removes something from the Queue" do
-    skip
     q = Queue.new
     q.enqueue(5)
     removed = q.dequeue
@@ -42,7 +38,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     q = Queue.new
     q.enqueue(5)
     q.enqueue(3)
@@ -53,24 +48,33 @@
   end
 
   it "properly adjusts the size with enqueueing and dequeueing" do
-    skip
     q = Queue.new
     q.empty?.must_equal true
+    q.size.must_equal 0
     q.enqueue(-1)
     q.enqueue(-60)
     q.empty?.must_equal false
+    q.size.must_equal 2
     q.dequeue
     q.dequeue
     q.empty?.must_equal true
+    q.size.must_equal 0
   end
 
   it "returns the front element in the Queue" do
-    skip
     q = Queue.new
     q.enqueue(40)
     q.enqueue(22)
     q.enqueue(3)
     q.dequeue
+    expect(q.front).must_equal 22
     expect(q.dequeue).must_equal 22
   end
+
+  it "raises an error if buffer is full" do
+    q = Queue.new(2)
+    q.enqueue(40)
+    q.enqueue(22)
+    expect{q.enqueue(3)}.must_raise
+  end
 end

test/stack_test.rb

@@ -10,14 +10,14 @@
   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 +26,11 @@
   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 +39,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     s = Stack.new
     s.push(5)
     s.push(3)