Ejercicio 14

exercises/ex14/dllist.py

@@ -0,0 +1,134 @@
+class DoubleLinkedListNode(object):
+    def __init__(self, value, prev, nxt):
+        self.value = value
+        self.next = nxt
+        self.prev = prev
+
+    def __repr__(self):
+        nval = self.next and self.next.value or None
+        pval = self.prev and self.prev.value or None
+        return f"[{repr(pval)}, {self.value}, {repr(nval)}]"
+
+
+class DoubleLinkedList(object):
+    def __init__(self):
+        self.begin = None
+        self.end = None
+
+    def count(self):
+        """
+        Returns number of items.
+        Regresa la cantidad de ítems.
+        """
+        count = 0
+        node = self.begin
+        while node:
+            count += 1
+            node = node.next
+        return count
+
+    def push(self, obj):
+        """
+        Appends a new item on the end of the list.
+        Añade un nuevo ítem al final de la lista.
+        """
+        node = DoubleLinkedListNode(obj, self.end, None)
+        if self.begin is None:
+            self.begin = node
+            self.end = self.begin
+        else:
+            self.end.next = node
+            self.end = node
+
+    def pop(self):
+        """
+        Removes the last item and returns its value.
+        Remueve el último ítem y regresa su valor.
+        """
+        if self.end is None:
+            value = None
+        else:
+            value = self.end.value
+            if self.end == self.begin:
+                self.end = self.begin = None
+            else:
+                self.end = self.end.prev
+                self.end.next = None
+        return value
+
+    def unshift(self):
+        """
+        Removes the first item and returns its value.
+        Remueve el primer ítem y regresa su valor.
+        """
+        if self.begin is None:
+            value = None
+        else:
+            value = self.begin.value
+            if self.begin == self.end:
+                self.begin = self.end = None
+            else:
+                self.begin = self.begin.next
+                self.begin.prev = None
+        return value
+
+    def shift(self, obj):
+        """
+        Appends a new item on the begin of the list.
+        Añade un nuevo ítem al inicio de la lista.
+        """
+        node = DoubleLinkedListNode(obj, None, self.begin)
+        if self.begin is None:
+            self.begin = node
+            self.end = self.begin
+        else:
+            self.begin.prev = node
+            self.begin = node
+
+    def remove(self, obj):
+        """
+        Removes a item by its value and return its list index.
+        Remueve un ítem según su valor y regresa su índice en la lista.
+        """
+        count = 0
+        node = self.begin
+        while node.next:
+            if obj == node.value:
+                break
+            count += 1
+            node = node.next
+        if node.next:
+            node.value = node.next.value
+            node.next = node.next.next
+        else:
+            node.value = node.next = node.prev = node = None
+        return count
+
+    def get(self, index):
+        """
+        Returns item value at list index.
+        Regresa el valor del ítem en el índice de la lista.
+        """
+        count = 0
+        node = self.begin
+        while count != index:
+            count += 1
+            node = node.next
+        if node:
+            return node.value
+        else:
+            return None
+
+    def first(self):
+        """
+        Returns value of first item.
+        Regresa el valor del primer ítem.
+        """
+        return self.begin.value
+
+    def last(self):
+        """
+        Returns value of last item.
+        Regresa el valor del último ítem.
+        """
+        return self.end.value

exercises/ex14/test_dllist.py

@@ -0,0 +1,97 @@
+from dllist import DoubleLinkedList
+
+
+def test_push():
+    colors = DoubleLinkedList()
+    colors.push("Pthalo Blue")
+    assert colors.count() == 1
+    colors.push("Ultramarine Blue")
+    assert colors.count() == 2
+
+
+def test_pop():
+    colors = DoubleLinkedList()
+    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
+
+
+def test_get():
+    colors = DoubleLinkedList()
+    colors.push("Vermillion")
+    assert colors.get(0) == "Vermillion"
+    colors.push("Sap Green")
+    assert colors.get(0) == "Vermillion"
+    assert colors.get(1) == "Sap Green"
+    colors.push("Cadmium Yellow Light")
+    assert colors.get(0) == "Vermillion"
+    assert colors.get(1) == "Sap Green"
+    assert colors.get(2) == "Cadmium Yellow Light"
+    assert colors.pop() == "Cadmium Yellow Light"
+    assert colors.get(0) == "Vermillion"
+    assert colors.get(1) == "Sap Green"
+    assert colors.get(2) is None
+    colors.pop()
+    assert colors.get(0) == "Vermillion"
+    colors.pop()
+    assert colors.get(0) is None
+
+
+def test_unshift():
+    colors = DoubleLinkedList()
+    colors.push("Viridian")
+    colors.push("Sap Green")
+    colors.push("Van Dyke")
+    assert colors.unshift() == "Viridian"
+    assert colors.unshift() == "Sap Green"
+    assert colors.unshift() == "Van Dyke"
+    assert colors.unshift() is None
+    assert colors.count() == 0
+
+
+def test_shift():
+    colors = DoubleLinkedList()
+    colors.shift("Cadmium Orange")
+    assert colors.count() == 1
+    colors.shift("Carbazole Violet")
+    assert colors.count() == 2
+    assert colors.pop() == "Cadmium Orange"
+    assert colors.count() == 1
+    assert colors.pop() == "Carbazole Violet"
+    assert colors.count() == 0
+
+
+def test_first():
+    colors = DoubleLinkedList()
+    colors.push("Cadmium Red Light")
+    assert colors.first() == "Cadmium Red Light"
+    colors.push("Hansa Yellow")
+    assert colors.first() == "Cadmium Red Light"
+    colors.shift("Pthalo Green")
+    assert colors.first() == "Pthalo Green"
+
+
+def test_last():
+    colors = DoubleLinkedList()
+    colors.push("Cadmium Red Light")
+    assert colors.last() == "Cadmium Red Light"
+    colors.push("Hansa Yellow")
+    assert colors.last() == "Hansa Yellow"
+    colors.shift("Pthalo Green")
+    assert colors.last() == "Hansa Yellow"
+
+
+def test_remove():
+    colors = DoubleLinkedList()
+    colors.push("Cobalt")
+    colors.push("Zinc White")
+    colors.push("Nickle Yellow")
+    colors.push("Perinone")
+    assert colors.remove("Cobalt") == 0
+    assert colors.remove("Perinone") == 2
+    assert colors.remove("Nickle Yellow") == 1
+    assert colors.remove("Zinc White") == 0