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Create Deque #118

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166 changes: 166 additions & 0 deletions Programs/Deque
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# Python implementation of De-queue using circular
# array

# A structure to represent a Deque
MAX = 100


class Deque:
def __init__(self, size):
self.arr = [0] * MAX
self.front = -1
self.rear = 0
self.size = size

''' Operations on Deque:
void insertfront(int key);
void insertrear(int key);
void deletefront();
void deleterear();
bool isFull();
bool isEmpty();
int getFront();
int getRear(); '''

# Checks whether Deque is full or not.
def isFull(self):
return ((self.front == 0 and self.rear == self.size-1) or self.front == self.rear + 1)

# Checks whether Deque is empty or not.

def isEmpty(self):
return (self.front == -1)

# Inserts an element at front
def insertfront(self, key):

# check whether Deque if full or not
if (self.isFull()):
print("Overflow")
return

# If queue is initially empty
if (self.front == -1):
self.front = 0
self.rear = 0

# front is at first position of queue
elif (self.front == 0):
self.front = self.size - 1

else: # decrement front end by '1'
self.front = self.front-1

# insert current element into Deque
self.arr[self.front] = key

# function to inset element at rear end
# of Deque.

def insertrear(self, key):
if (self.isFull()):
print(" Overflow")
return

# If queue is initially empty
if (self.front == -1):
self.front = 0
self.rear = 0

# rear is at last position of queue
elif (self.rear == self.size-1):
self.rear = 0

# increment rear end by '1'
else:
self.rear = self.rear+1

# insert current element into Deque
self.arr[self.rear] = key

# Deletes element at front end of Deque

def deletefront(self):
# check whether Deque is empty or not
if (self.isEmpty()):
print("Queue Underflow")
return

# Deque has only one element
if (self.front == self.rear):
self.front = -1
self.rear = -1

else:
# back to initial position
if (self.front == self.size - 1):
self.front = 0

else: # increment front by '1' to remove current
# front value from Deque
self.front = self.front+1

# Delete element at rear end of Deque

def deleterear(self):
if (self.isEmpty()):
print(" Underflow")
return

# Deque has only one element
if (self.front == self.rear):
self.front = -1
self.rear = -1

elif (self.rear == 0):
self.rear = self.size-1
else:
self.rear = self.rear-1

# Returns front element of Deque

def getFront(self):
# check whether Deque is empty or not
if (self.isEmpty()):
print(" Underflow")
return -1

return self.arr[self.front]

# function return rear element of Deque

def getRear(self):
# check whether Deque is empty or not
if(self.isEmpty() or self.rear < 0):
print(" Underflow")
return -1

return self.arr[self.rear]


# Driver code
if __name__ == "__main__":
dq = Deque(5)

# Function calls
print("Insert element at rear end : 5 ")
dq.insertrear(5)

print("insert element at rear end : 10 ")
dq.insertrear(10)

print(f"get rear element : {dq.getRear()}")

dq.deleterear()
print(f"After delete rear element new rear become : {dq.getRear()}")

print("inserting element at front end")
dq.insertfront(15)

print(f"get front element: {dq.getFront()}")

dq.deletefront()

print(f"After delete front element new front become : {dq.getFront()}")

# This code is contributed by _saurabh_jaiswal