Ejercicios 15a y 15b arreglados

exercises/ex15/queue.py

@@ -1,5 +1,5 @@
 class QueueNode(object):
-    def __init__(self, value, prev, nxt):
+    def __init__(self, prev, value, nxt):
         self.value = value
         self.next = nxt
         self.prev = prev
@@ -24,7 +24,7 @@ class Queue(object):
         node = self.begin
         while node:
             count += 1
-            node = node.next
+            node = node.prev
         return count
 
     def unshift(self):
@@ -36,11 +36,11 @@ class Queue(object):
             value = None
         else:
             value = self.begin.value
-            if self.begin == self.end:
+            if self.begin.prev is None:
                 self.begin = self.end = None
             else:
-                self.begin = self.begin.next
-                self.begin.prev = None
+                self.begin = self.begin.prev
+                self.begin.next = None
         return value
 
     def shift(self, obj):
@@ -48,24 +48,30 @@ class Queue(object):
         Appends a new item on the begin of the list.
         Añade un nuevo ítem al inicio de la lista.
         """
-        node = QueueNode(obj, None, self.begin)
+        node = QueueNode(None, obj, self.begin)
         if self.begin is None:
             self.begin = node
             self.end = self.begin
         else:
-            self.begin.prev = node
-            self.begin = node
+            self.begin.prev = self.end = node
 
-    def top(self):
+    def drop(self):
+        """
+        Removes the last item and returns its value.
+        Remueve el último ítem y regresa su valor.
+        """
+        value = self.end and self.end.value or None
+        if value:
+            if self.end.next is None:
+                self.begin = self.end = None
+            else:
+                self.end = self.end.next
+                self.end.prev = None
+        return value
+
+    def first(self):
         """
         Returns value of first item.
         Regresa el valor del primer ítem.
         """
-        return self.begin.value
-
-    def bottom(self):
-        """
-        Returns value of last item.
-        Regresa el valor del último ítem.
-        """
-        return self.end.value
+        return self.begin and self.begin.value or None

exercises/ex15/test_queue.py

@@ -1,45 +1,40 @@
 from queue import Queue
 
 
-def test_unshift():
-    colors = Queue()
-    colors.shift("Viridian")
-    colors.shift("Sap Green")
-    colors.shift("Van Dyke")
-    assert colors.unshift() == "Van Dyke"
-    assert colors.unshift() == "Sap Green"
-    assert colors.unshift() == "Viridian"
-    assert colors.unshift() is None
-    assert colors.count() == 0
-
-
 def test_shift():
     colors = Queue()
-    colors.shift("Cadmium Orange")
+    colors.shift("Pthalo Blue")
     assert colors.count() == 1
-    colors.shift("Carbazole Violet")
+    colors.shift("Ultramarine Blue")
     assert colors.count() == 2
-    assert colors.unshift() == "Carbazole Violet"
+
+
+def test_unshift():
+    colors = Queue()
+    colors.shift("Magenta")
+    colors.shift("Alizarin")
+    assert colors.unshift() == "Magenta"
+    assert colors.unshift() == "Alizarin"
+    assert colors.unshift() is None
+
+
+def test_first():
+    colors = Queue()
+    colors.shift("Cadmium Red Light")
+    assert colors.first() == "Cadmium Red Light"
+    colors.shift("Hansa Yellow")
+    assert colors.first() == "Cadmium Red Light"
+    colors.shift("Pthalo Green")
+    assert colors.first() == "Cadmium Red Light"
+
+
+def test_drop():
+    colors = Queue()
+    colors.shift("Cad Red")
+    colors.shift("Hansa Yellow")
+    assert colors.count() == 2
+    colors.drop()
     assert colors.count() == 1
-    assert colors.unshift() == "Cadmium Orange"
-    assert colors.count() == 0
-
-
-def test_top():
-    colors = Queue()
-    colors.shift("Cadmium Red Light")
-    assert colors.top() == "Cadmium Red Light"
-    colors.shift("Hansa Yellow")
-    assert colors.top() == "Hansa Yellow"
-    colors.shift("Pthalo Green")
-    assert colors.top() == "Pthalo Green"
-
-
-def test_bottom():
-    colors = Queue()
-    colors.shift("Cadmium Red Light")
-    assert colors.bottom() == "Cadmium Red Light"
-    colors.shift("Hansa Yellow")
-    assert colors.bottom() == "Cadmium Red Light"
-    colors.shift("Pthalo Green")
-    assert colors.bottom() == "Cadmium Red Light"
+    assert colors.first() == "Cad Red"
+    colors.drop()
+    assert colors.first() is None

exercises/ex15/test_stack.py

@@ -14,9 +14,7 @@ def test_pop():
     colors.push("Magenta")
     colors.push("Alizarin")
     assert colors.pop() == "Alizarin"
-    assert colors.count() == 1
     assert colors.pop() == "Magenta"
-    assert colors.count() == 0
     assert colors.pop() is None
 
 
@@ -26,7 +24,5 @@ def test_top():
     assert colors.top() == "Cadmium Red Light"
     colors.push("Hansa Yellow")
     assert colors.top() == "Hansa Yellow"
-    colors.pop()
-    assert colors.top() == "Cadmium Red Light"
-    colors.pop()
-    assert colors.top() is None
+    colors.push("Pthalo Green")
+    assert colors.top() == "Pthalo Green"