solved: sol1 with a doubly linked-list -@iamserda

neetcodeio/algostructybeginners/Lv2-LinkedLists/queues.py

@@ -0,0 +1,116 @@
+"""
+title: Design a Doube-Ended Queue
+url: https://neetcode.io/problems/queue
+owner: neetcode.io
+desicription: double-ended queue using a doubly-linked-list
+solver: @iamserda
+"""
+
+class Node:
+    def __init__(self, val):
+        self.val = val
+        self.prv = None
+        self.nxt = None
+
+
+class Deque:
+
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def isEmpty(self) -> bool:
+        if not self.head:
+            return True
+        return False
+
+    def append(self, value: int) -> None:
+        new_node = Node(value)
+        if not self.head:
+            self.head = new_node
+            self.tail = new_node
+        else:
+            new_node.prv = self.tail
+            self.tail.nxt = new_node
+            self.tail = self.tail.nxt
+
+    def appendleft(self, value: int) -> None:
+        new_node = Node(value)
+        if not self.head:
+            self.tail = new_node
+            self.head = new_node
+        else:
+            new_node.nxt = self.head
+            self.head.prv = new_node
+            self.head = new_node
+
+    def pop(self) -> int:
+        if self.tail:
+            removed = self.tail
+            if self.tail.prv:
+                self.tail = self.tail.prv
+                self.tail.nxt = None
+                removed.prv = None
+            else:
+                self.head = self.tail = None
+            return removed.val
+        return -1
+
+    def popleft(self) -> int:
+        if not self.head:
+            return -1
+        if self.head == self.tail:
+            removed = self.head
+            self.head = self.tail = None
+            return removed.val
+        removed = self.head
+        self.head = self.head.nxt
+        self.head.prv = None
+        removed.nxt = None
+        return removed.val
+
+
+# Testing Arena:
+myQueue = Deque()
+mydict = {
+    "append": myQueue.append,
+    "appendLeft": myQueue.appendleft,
+    "isEmpty": myQueue.isEmpty,
+    "pop": myQueue.pop,
+    "popLeft": myQueue.popleft,
+}
+
+# transactions
+transactions = [
+    ("isEmpty", None),
+    ("append", 10),
+    ("isEmpty", None),
+    ("appendLeft", 20),
+    ("popLeft", None),
+    ("pop", None),
+    ("pop", None),
+    ("append", 30),
+    ("pop", None),
+    ("isEmpty", None),
+]
+
+# Output:
+expected = [True, None, False, None, 20, 10, -1, None, 30, True]
+output = []
+
+for transaction in transactions:
+    if isinstance(transaction, tuple):
+        method = mydict[transaction[0]]
+        param = transaction[1]
+        if param:
+            output.append(method(param))
+        else:
+            output.append(method())
+    else:
+        raise TypeError(
+            "Wrong datatype: expecting either of string or a tuple of size 2."
+        )
+if len(expected) == len(output):
+    results = True
+    for index in range(len(expected)):
+        assert expected[index] == output[index]