def sort_stack(stack):
if stack.size() == 0:
return stack
temp_stack = Stack.new()
while not stack.is_empty():
element = stack.pop()
while not temp_stack.is_empty() and temp_stack.peek() > element:
temp_stack_element = temp_stack.pop()
stack.push(temp_stack_element)
temp_stack.push(element)
return temp_stack
def is_palindrome(list):
if not list.head():
return True # Empty lists are empty strings, and as such they are palindromes.
fast_runner = list.head()
slow_runner = list.head()
reversed_half = Stack.new()
i = 0
# Position slow runner in the middle of the linked list.
while fast_runner is not None:
fast_runner = fast_runner.next_element()
i += 1
if i % 2 == 0:
reversed_half.push(slow_runner)
slow_runner = slow_runner.next_element()
if i % 2 != 0: # Edge case for odd length linked lists.
reversed_half.push(slow_runner)
while slow_runner is not None:
elem = reversed_half.pop()
if slow_runner.data() != elem.data():
return False
slow_runner = slow_runner.next_element()
return True
def __init__(self, size_limit):
if size_limit <= 0:
raise ValueError("Stack size limit needs to be positive.")
self._size_limit = size_limit
self._stack = Stack.new()
def __init__(self):
self._newest_elements = Stack.new()
self._oldest_elements = Stack.new()
def __init__(self, index):
self._disks = Stack.new()
self._index = index