Circular Queue | Python div-bargali#233

Circular Queue | Python

Author: div-bargali

Python/Data-Structures/Circular Queue/CircQueue.py

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+class CircQueue:
+ """
+ Implementation of circular, array-backed queue data structure
+ """
+
+ # circular queue keeps track of position of recently enqueued item and
+ # position of next item to dequeue
+ def __init__(self, limit=20):
+ self.data = [None] * limit
+ self.head = -1
+ self.tail = -1
+
+ # add item into the queue
+ def enqueue(self, val):
+ if (self.tail + 1) % len(self.data) == self.head:
+ raise RuntimeError
+
+ if self.head == self.tail == -1:
+ self.tail = 0
+ self.head = 0
+ else:
+ self.tail = (self.tail + 1) % len(self.data)
+
+ self.data[self.tail] = val
+
+ # remove and return the first item in the queue (first in first out)
+ def dequeue(self):
+ if self.head == -1:
+ raise RuntimeError
+
+ data = self.data[self.head]
+ self.data[self.head] = None
+
+ if self.head == self.tail:
+ self.head = -1
+ self.tail = -1
+ else:
+ self.head = (self.head + 1) % len(self.data)
+
+ return data
+
+ # resize data array to given size
+ def resize(self, newsize):
+ assert newsize > len(self.data)
+
+ new_data = []
+ for item in self:
+ new_data.append(item)
+
+ self.tail = len(new_data) - 1
+
+ for _ in range(newsize - len(self.data)):
+ new_data.append(None)
+
+ self.data = new_data
+ self.head = 0
+
+ # return True if queue is empty, otherwise False
+ def empty(self):
+ for item in self.data:
+ if item is not None:
+ return False
+ return True
+
+ # return True if queue is not empty, otherwise False
+ def __bool__(self):
+ return not self.empty()
+
+ # return all data in queue in a string
+ def __str__(self):
+ if not self:
+ return ''
+ return ', '.join(str(item) for item in self)
+
+ # return all data in queue in a string
+ def __repr__(self):
+ return str(self)
+
+ # iter through the queue
+ def __iter__(self):
+ idx = self.head
+ while idx != self.tail:
+ yield self.data[idx]
+ idx = (idx + 1) % len(self.data)
+ yield self.data[idx]
+
+
+# print option menu and take user input
+def option_menu():
+ print("1. Enqueue")
+ print("2. Dequeue")
+ print("3. Resize Queue")
+ print("4. Print Queue")
+ print("5. Exit")
+
+ try:
+ option = int(input("Enter option: "))
+ return option
+
+ except Exception as e:
+ print(f"ERROR: {e}\n")
+
+# test function
+def test():
+ q = CircQueue()
+
+ while True:
+ option = option_menu()
+
+ if option == 1:
+ while True:
+ try:
+ item = int(input("Enter value to enqueue (enter character to quit): "))
+ q.enqueue(item)
+ except:
+ print()
+ break
+
+ elif option == 2:
+ print("Result of dequeue: ", q.dequeue(), "\n")
+
+ elif option == 3:
+ new_size = int(input("Enter new size: "))
+ q.resize(new_size)
+
+ elif option == 4:
+ print("Current queue: ", q)
+ print("Current queue data: ", q.data, "\n")
+
+ elif option == 5:
+ print("Exiting...")
+ break
+
+ else:
+ print("Invalid option\n")
+
+if __name__ == "__main__":
+ test()