RecursionError in my program while trying to reverse a stack using append,empty() and pop and without iterations

Question

import sys
import os

Reversing a stack using empty pop and append and without iterations.

we will use recursive call.

def insert_element_at_bottom(stack, item):
    if isEmpty(stack):
        push(stack, item)
    else:
        temp = pop(stack)
        insert_element_at_bottom(stack, item)
        push(stack, temp)

def create_stack():
    stack = []
    return stack


def push(stack, item):
    stack.append(item)


def pop(stack):
    if isEmpty(stack):
        print("stack underflow")
        exit(1)
        return stack.pop()


def isEmpty(stack):
    return len(stack) == 0


def reverse_stack(stack):
    if not isEmpty(stack):
        temp = pop(stack)
        reverse_stack(stack)
        insert_element_at_bottom(stack, temp)


def print_stack(stack):
    for i in range(len(stack) - 1, -1, -1):
        print(stack[i], end=' ')
    print()

driver code

stack = create_stack()
push(stack, str(4))
push(stack, str(3))
push(stack, str(2))
push(stack, str(1))
print("Original stack:")
reverse_stack(stack)
print("Reversed stack:")
print_stack(stack)

I am getting an error:

RecursionError: maximum recursion depth exceeded while calling a Python object.

this is your answer that you expected?

Beny Gj
– Beny Gj

2020-05-06 09:24:19 +00:00
Commented May 6, 2020 at 9:24 — Beny Gj
– Beny Gj, Commented May 6, 2020 at 9:24
Thanks a lot @BenyGj.

mtr_007
– mtr_007

2020-05-06 13:22:46 +00:00
Commented May 6, 2020 at 13:22 — mtr_007
– mtr_007, Commented May 6, 2020 at 13:22

Beny Gj · Accepted Answer · 2020-05-06 08:10:14Z

1

hi you need to change your reverse_stack you omit to stop the recursion

you can do something like that:

def reverse_stack(stack_q, len_s= None): 

        if len_s is None: 
            len_s = len(stack_q) 
        if len_s in  (0, 1): 
            return  

        stack_q.insert(len(stack_q) - len_s,  stack_q.pop()) 

        len_s -=1        
        reverse_stack(stack_q, len_s)

let's try it:

a = list(range(1, 10))
a                          
[1, 2, 3, 4, 5, 6, 7, 8, 9]

reverse_stack(a)
a                          
[9, 8, 7, 6, 5, 4, 3, 2, 1]

edited May 6, 2020 at 8:10

answered May 6, 2020 at 8:04

Beny Gj

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1 Comment

mtr_007 Over a year ago

Thanks a lot @Beny Gj.The change you suggested is insightful.

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RecursionError in my program while trying to reverse a stack using append,empty() and pop and without iterations

Reversing a stack using empty pop and append and without iterations.

we will use recursive call.

driver code

I am getting an error:

RecursionError: maximum recursion depth exceeded while calling a Python object.

1 Answer 1

1 Comment

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Collectives™ on Stack Overflow

Reversing a stack using empty pop and append and without iterations.

we will use recursive call.

driver code

I am getting an error:

RecursionError: maximum recursion depth exceeded while calling a Python object.

1 Answer 1

1 Comment

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