This notebook was prepared by Donne Martin. Source and license info is on GitHub.

# Challenge Notebook¶

## Constraints¶

• Are the stacks and array a fixed size?
• Yes
• Are the stacks equally sized?
• Yes
• Does pushing to a full stack result in an exception?
• Yes
• Does popping from an empty stack result in an exception?
• Yes
• Can we assume the user passed in stack index is valid?
• Yes
• Can we assume this fits memory?
• Yes

## Test Cases¶

• Test the following on the three stacks:
• Push to full stack -> Exception
• Push to non-full stack
• Pop on empty stack -> Exception
• Pop on non-empty stack

## Algorithm¶

Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

## Code¶

In [ ]:
class Stacks(object):

def __init__(self, num_stacks, stack_size):
# TODO: Implement me
pass

def abs_index(self, stack_index):
# TODO: Implement me
pass

def push(self, stack_index, data):
# TODO: Implement me
pass

def pop(self, stack_index):
# TODO: Implement me
pass


## Unit Test¶

The following unit test is expected to fail until you solve the challenge.

In [ ]:
# %load test_n_stacks.py
import unittest

class TestStacks(unittest.TestCase):

def test_pop_on_empty(self, num_stacks, stack_size):
print('Test: Pop on empty stack')
stacks = Stacks(num_stacks, stack_size)
stacks.pop(0)

def test_push_on_full(self, num_stacks, stack_size):
print('Test: Push to full stack')
stacks = Stacks(num_stacks, stack_size)
for i in range(0, stack_size):
stacks.push(2, i)
stacks.push(2, stack_size)

def test_stacks(self, num_stacks, stack_size):
print('Test: Push to non-full stack')
stacks = Stacks(num_stacks, stack_size)
stacks.push(0, 1)
stacks.push(0, 2)
stacks.push(1, 3)
stacks.push(2, 4)

print('Test: Pop on non-empty stack')
self.assertEqual(stacks.pop(0), 2)
self.assertEqual(stacks.pop(0), 1)
self.assertEqual(stacks.pop(1), 3)
self.assertEqual(stacks.pop(2), 4)

print('Success: test_stacks\n')

def main():
num_stacks = 3
stack_size = 100
test = TestStacks()
test.assertRaises(Exception, test.test_pop_on_empty, num_stacks,
stack_size)
test.assertRaises(Exception, test.test_push_on_full, num_stacks,
stack_size)
test.test_stacks(num_stacks, stack_size)

if __name__ == '__main__':
main()


## Solution Notebook¶

Review the Solution Notebook for a discussion on algorithms and code solutions.