StackRecursion.py

# Python program to reverse a 
# stack using recursion

# Recursive funtion that
# inserts an element
# at the bottom of a stack.
definsertAtBottom(stack, item):
ifisEmpty(stack):
push(stack, item)
else:
value=pop(stack)
insertAtBottom(stack, item)
push(stack, value)

# Below is the function that
# reverses the given stack
# using insertAtBottom()
defreverse(stack):
ifnotisEmpty(stack):
value=pop(stack)
reverse(stack)
insertAtBottom(stack, value)

# Function to create a stack.
# It initializes size of a stack as 0
defcreateStack():
stack= []
returnstack

# Function to check if
# the stack is empty
defisEmpty(stack):
returnlen(stack) ==0

# Function to push an
# item to stack
defpush(stack, item):
stack.append(item)

# Function to pop an 
# item from stack
defpop(stack):
# if stack is empty
# then error
if(isEmpty(stack)):
print("Stack Underflow!")
exit(1)

returnstack.pop()

# Function to print the stack
defprints(stack):
foriinrange(len(stack) -1, -1, -1):
print(stack[i], end=' ')

stack=createStack()
push( stack, str(4) )
push( stack, str(3) )
push( stack, str(2) )
push( stack, str(1) )
print("Original Stack ")
prints(stack)

reverse(stack)

print("Reversed Stack \n")
prints(stack)