Added queue.py

Author: VarunS2002

queue.py

@@ -0,0 +1,139 @@
+from typing import Optional
+
+
+class _BaseQueue:
+    class _EmptyQueueError(Exception):
+        def __str__(self) -> str:
+            return "Queue is empty."
+
+    def __init__(self) -> None:
+        self._data: list[Optional[object]] = [None] * 10
+        self._size: int = 0
+
+    def __len__(self) -> int:
+        return self._size
+
+    def length(self) -> int:
+        return self.__len__()
+
+    def __str__(self) -> str:
+        return str(self._data)
+
+    def is_empty(self) -> bool:
+        return self._size == 0
+
+
+class SingleEndedQueue(_BaseQueue):
+    def __init__(self) -> None:
+        super().__init__()
+        self._front: int = 0
+
+    def __eq__(self, other: 'SingleEndedQueue') -> bool:
+        if self.__class__ == other.__class__:
+            if self._data == other._data and self._front == other._front:
+                return True
+        return False
+
+    def first(self) -> Optional[object]:
+        if self.is_empty():
+            raise self._EmptyQueueError
+        return self._data[self._front]
+
+    def _resize(self, capacity: int) -> None:
+        old: list[Optional[object]] = self._data
+        self._data = [None] * capacity
+        walk: int = self._front
+        for k in range(self._size):
+            self._data[k] = old[walk]
+            walk = (1 + walk) % len(old)
+        self._front = 0
+
+    def enqueue_back(self, element: Optional[object]) -> None:
+        if self._size == len(self._data):
+            self._resize(2 * len(self._data))
+        avail: int = (self._front + self._size) % len(self._data)
+        self._data[avail] = element
+        self._size += 1
+
+    def dequeue_front(self) -> Optional[object]:
+        if self.is_empty():
+            raise self._EmptyQueueError
+        element: Optional[object] = self._data[self._front]
+        self._data[self._front] = None
+        self._front = (self._front + 1) % len(self._data)
+        self._size -= 1
+        return element
+
+
+class DoubleEndedQueue(SingleEndedQueue):
+    def __init__(self) -> None:
+        super().__init__()
+        self._back = 0
+
+    def __eq__(self, other: 'DoubleEndedQueue') -> bool:
+        if self.__class__ == other.__class__:
+            if self._data == other._data and self._front == other._front and self._back == other._back:
+                return True
+        return False
+
+    def last(self) -> Optional[object]:
+        if self.is_empty():
+            raise self._EmptyQueueError
+        return self._data[self._back]
+
+    def _resize(self, capacity: int) -> None:
+        super(DoubleEndedQueue, self)._resize(capacity)
+        self._back = (self._front + self._size - 1) % len(self._data)
+
+    def enqueue_back(self, element: Optional[object]) -> None:
+        super(DoubleEndedQueue, self).enqueue_back(element)
+        self._back = (self._front + self._size - 1) % len(self._data)
+
+    def dequeue_front(self) -> Optional[object]:
+        element: Optional[object] = super(DoubleEndedQueue, self).dequeue_front()
+        self._back = (self._front + self._size - 1) % len(self._data)
+        return element
+
+    def enqueue_front(self, element: Optional[object]) -> None:
+        if self._size == len(self._data):
+            self._resize(2 * len(self._data))
+        self._front = (self._front - 1) % len(self._data)
+        self._data[self._front] = element
+        self._size += 1
+        self._back = (self._front + self._size - 1) % len(self._data)
+
+    def dequeue_back(self) -> Optional[object]:
+        if self.is_empty():
+            raise self._EmptyQueueError
+        back: int = (self._front + self._size - 1) % len(self._data)
+        element: Optional[object] = self._data[back]
+        self._data[back] = None
+        self._size -= 1
+        self._back = (self._front + self._size - 1) % len(self._data)
+        return element
+
+
+if __name__ == '__main__':
+    print("1. Single Ended Queue")
+    print("2. Double Ended Queue")
+    mode = int(input("Choose:"))
+    if mode == 1:
+        single_ended_queue = SingleEndedQueue()
+        for i in range(1, 11):
+            single_ended_queue.enqueue_back("f_" + str(i))
+        print(single_ended_queue.first())
+        print(single_ended_queue.dequeue_front())
+        single_ended_queue.enqueue_back("f_" + str(11))
+        print(single_ended_queue.first())
+        print(single_ended_queue)
+    elif mode == 2:
+        double_ended_queue = DoubleEndedQueue()
+        for i in range(1, 6):
+            double_ended_queue.enqueue_back("f_" + str(i))
+        print(double_ended_queue.first())
+        print(double_ended_queue.dequeue_front())
+        double_ended_queue.enqueue_front("f_" + str(1))
+        print(double_ended_queue.first())
+        print(double_ended_queue.last())
+        print(double_ended_queue.dequeue_back())
+        print(double_ended_queue.last())