def stack_split_alt(source):
"""
-------------------------------------------------------
Splits the source stack into separate target stacks.
When finished source stack is empty. Values are
pushed alternately onto the returned target stacks.
Use: target1, target2 = stack_split_alt(source)
-------------------------------------------------------
Parameters:
source - the stack to split into two parts (Stack)
Returns:
target1 - contains alternating values from source (Stack)
target2 - contains other alternating values from source (Stack)
-------------------------------------------------------
"""
target1 = Stack()
target2 = Stack()
i = 1
while source.is_empty() == False:
if i == 1:
target1.push(source.pop())
i = 2
elif i == 2:
target2.push(source.pop())
i = 1
return target1, target2
def postfix(string):
"""
-------------------------------------------------------
Evaluates a postfix expression.
Use: answer = postfix(string)
-------------------------------------------------------
Parameters:
string - the postfix string to evaluate (str)
Returns:
answer - the result of evaluating string (float)
-------------------------------------------------------
"""
string = string.split(" ")
r = Stack()
for i in string:
if i.isdigit():
r.push(i)
elif i in OPERATORS:
if i == "+":
r.push(float(r.pop()) + float(r.pop()))
elif i == "-":
x = float(r.pop())
y = float(r.pop())
r.push(y - x)
elif i == "*":
r.push(float(r.pop()) * float(r.pop()))
elif i == "/":
r.push(float(r.pop()) / float(r.pop()))
answer = r.pop()
return answer
def stack_combine(source1, source2):
"""
-------------------------------------------------------
Combines two source stacks into a target stack.
When finished, the contents of source1 and source2 are interlaced
into target and source1 and source2 are empty.
Use: target = stack_combine(source1, source2)
-------------------------------------------------------
Parameters:
source1 - a stack (Stack)
source2 - another stack (Stack)
Returns:
target - the contents of the source1 and source2
are interlaced into target (Stack)
-------------------------------------------------------
"""
target = Stack()
i = 1
while source1.is_empty() == False or source2.is_empty() == False:
if i == 1:
target.push(source1.pop())
if source2.is_empty() == False:
i = 2
elif i == 2:
target.push(source2.pop())
if source1.is_empty() == False:
i = 1
return target
def stack_test(source):
"""
-------------------------------------------------------
Tests the methods of Stack for empty and
non-empty stacks using the data in source:
is_empty, push, pop, peek
(Testing pop and peek while empty throws exceptions)
Use: stack_test(source)
-------------------------------------------------------
Parameters:
source - list of data (list of ?)
Returns:
None
-------------------------------------------------------
"""
stack = Stack()
print('Test is empty?')
print(stack.is_empty())
print(array_to_stack(stack, source))
print('Test is empty?')
print(stack.is_empty())
print('Test for peek value: ')
print(stack.peek())
print('Test for push value: ')
stack.push(1)
print('Test for peek value: ')
print(stack.peek())
print('Test for pop value: ')
stack.pop()
print('Test is empty?')
print(stack.is_empty())
print('Test for peek value: ')
print(stack.peek())
def mirror(string):
b = True
stack = Stack()
n = len(string)
i = 0
while b and string[i] != MID:
if string[i] in CHARS:
stack.push(string[i])
i += 1
else:
b = False
i += 1 # Skip MID
while b and i < n:
if stack.is_empty():
b = False
else:
c = stack.pop()
if not c == string[i]:
b = False
else:
i += 1
return b
def is_palindrome_stack(string):
"""
-------------------------------------------------------
Determines if string is a palindrome. Ignores case, digits, spaces, and
punctuation in string.
Use: palindrome = is_palindrome_stack(string)
-------------------------------------------------------
Parameters:
string - a string (str)
Returns:
palindrome - True if string is a palindrome, False otherwise (bool)
-------------------------------------------------------
"""
palindrome = None
newstr = ""
s = Stack()
for i in string:
if i.isalnum():
newstr += i
for j in newstr:
s.push(j)
revstr = ""
for k in s:
revstr += s.pop()
if revstr.lower() == newstr.lower():
palindrome = True
else:
palindrome = False
return palindrome
def postfix(string):
"""
-------------------------------------------------------
Evaluates a postfix expression.
Use: answer = postfix(string)
-------------------------------------------------------
Parameters:
string - the postfix string to evaluate (str)
Returns:
answer - the result of evaluating string (float)
-------------------------------------------------------
"""
s = Stack()
ss = string.split()
for i in ss:
if i.isdigit():
s.push(i)
elif i in OPERATORS:
val1 = s.pop()
val2 = s.pop()
if i == "+":
s.push(float(int(val2) + int(val1)))
elif i == "-":
s.push(float(int(val2) - int(val1)))
elif i == "*":
s.push(float(int(val2) * int(val1)))
elif i == "/":
s.push(float(int(val2) / int(val1)))
answer = s.pop()
return answer
def stack_test(source):
"""
-------------------------------------------------------
Tests the methods of Stack for empty and
non-empty stacks using the data in source:
is_empty, push, pop, peek
(Testing pop and peek while empty throws exceptions)
Use: stack_test(source)
-------------------------------------------------------
Parameters:
source - list of data (list of ?)
Returns:
None
-------------------------------------------------------
"""
s = Stack()
# Test if stack is empty (Expected: TRUE)
print("Stack contents: ")
for i in s:
print(i, end=' ')
print("\tEmpty? {}".format(s.is_empty()))
# Load elements from source into Stack
print(">> Push elements from source onto stack")
print(">> Num elements to push: {}".format(len(source)))
for elem in source:
s.push(elem)
# Check if the Stack is empty again (T/F depending on source contents)
print("Stack contents: ")
for i in s:
print(i, end=' ')
print("\tEmpty? {}".format(s.is_empty()))
# Peek the top of the stack
top = None
try:
top = s.peek()
except:
print(">>! Peeked at an empty stack, assertion caught, continuing...")
# Check if top of stack is the end element of source
print("Top of stack should be same as end of list")
if s.is_empty():
print("List empty so no check")
else:
top_same = top == source[-1]
print("Top same as end of list?")
print("Top: {}\tEnd of list: {}".format(top, source[-1]))
print("Same? {}".format(top_same))
# Testing pop
try:
print(">> Pop top of stack")
popped = s.pop()
print("Popped value should be same as end of list.\tSame? {}".format(popped == source[-1]))
except:
print(">>! Popped from an empty stack, exception caught, continuing...")
return
def stack_test(source):
"""
-------------------------------------------------------
Tests the methods of Stack for empty and
non-empty stacks using the data in source:
is_empty, push, pop, peek
(Testing pop and peek while empty throws exceptions)
Use: stack_test(source)
-------------------------------------------------------
Parameters:
source - list of data (list of ?)
Returns:
None
-------------------------------------------------------
"""
s = Stack()
print("Stack Initialised")
print()
print(SEP)
print("Stack is_empty (expect True): {}".format(s.is_empty()))
print(SEP)
print("Add one item to Stack:")
s.push(source[0])
print("Top of Stack (peek):")
print(s.peek())
print(SEP)
print("Stack is_empty (expect False): {}".format(s.is_empty()))
print(SEP)
print("Stack pop:")
v = s.pop()
print(v)
print(SEP)
print("Stack is_empty (expect True): {}".format(s.is_empty()))
print(SEP)
print("Copy all data to Stack")
array_to_stack(s, source)
print(SEP)
print("Stack is_empty (expect False): {}".format(s.is_empty()))
print(SEP)
print("Top of Stack (peek):")
print(s.peek())
print(SEP)
print("Remove all elements from Stack")
while not s.is_empty():
v = s.pop()
print(v)
print()
print(SEP)
print("Stack is_empty (expect True): {}".format(s.is_empty()))
print()
return
def stack_maze(maze):
"""
-------------------------------------------------------
Solves a maze using Depth-First search.
Use: path = stack_maze(maze)
-------------------------------------------------------
Parameters:
maze - dictionary of points in a maze, where each point
represents a corridor end or a branch. Dictionary
keys are the name of the point followed by a list of
branches, if any. First point is named 'Start', exit
is named 'X' (dict)
Returns:
path - list of points visited before the exit is reached,
None if there is no exit (list of str)
-------------------------------------------------------
"""
s = Stack()
wrongpath = []
value = maze['Start']
exfi = False
for i in maze:
if 'X' in maze[i]:
path = []
exfi = False
elif exfi != False:
path = None
if path != None:
for i in value:
s.push(i)
value = s.pop()
path.append(value)
while value != 'X' and path != None:
value = maze[value]
while len(value) == 0:
value = s.pop()
for i in value:
if i in path:
_index = path.index(i)
wrongpath = path[_index + 1:]
path = path[:_index]
s.push(i)
value = s.pop()
path.append(value)
if value in wrongpath:
value = s.pop()
return path
def main():
source1 = Stack()
source2 = Stack()
l = [8, 12, 8, 5]
for v in l:
source1.push(v)
l2 = [14, 9, 7, 1, 6, 3]
for x in l2:
source2.push(x)
target = stack_combine(source1, source2)
for t in target:
print(t)
def main():
source1 = Stack()
source2 = Stack()
l = [8,12,8,5]
for v in l:
source1.push(v)
l2 = [14,9,7,1,6,3]
for x in l2:
source2.push(x)
stack = Stack()
stack.combine(source1, source2)
for s in stack:
print(s)
def has_balanced_brackets(string):
"""
-------------------------------------------------------
Determines if a string contains balanced brackets or not. Non-bracket
characters are ignored. Uses a stack. Brackets include {}, [], (), <>.
Use: balanced = has_balanced_brackets(string)
-------------------------------------------------------
Parameters:
string - the string to test (str)
Returns:
balanced (int) -
BALANCED if the brackets in string are balanced
MISMATCHED if the brackets in string are mismatched
MORE_RIGHT if there are more right brackets than left in string
MORE_LEFT if there are more left brackets than right in string
-------------------------------------------------------
"""
right = 0
left = 0
s = Stack()
for x in string:
if s.is_empty() == True:
s.push(x)
elif s.peek() == '[' and x == ']' or s.peek(
) == '(' and x == ')' or s.peek() == '{' and x == '}' or s.peek(
) == '<' and x == '>':
s.pop()
else:
s.push(x)
if s.is_empty() == True:
balanced = 0
else:
while s.is_empty() == False:
x = s.pop()
if x == '(' or x == '[' or x == '{' or x == '<':
left += 1
elif x == ')' or x == ']' or x == '}' or x == '>':
right += 1
if right > left:
balanced = 2
elif left > right:
balanced = 1
else:
balanced = 3
return balanced
def has_balanced_brackets(string):
"""
-------------------------------------------------------
Determines if a string contains balanced brackets or not. Non-bracket
characters are ignored. Uses a stack. Brackets include {}, [], (), <>.
Use: balanced = has_balanced_brackets(string)
-------------------------------------------------------
Parameters:
string - the string to test (str)
Returns:
balanced (int) -
BALANCED if the brackets in string are balanced
MISMATCHED if the brackets in string are mismatched
MORE_RIGHT if there are more right brackets than left in string
MORE_LEFT if there are more left brackets than right in string
-------------------------------------------------------
"""
s = Stack()
balanced = BALANCED
OPEN_BRACKETS = "([{<"
CLOSING_BRACKETS = ")]}>"
char_index = 0
while balanced == BALANCED and char_index < len(string):
# Get current character we are processing
char = string[char_index]
if char in OPEN_BRACKETS: # Push any opening bracket we see onto the stack
s.push(char)
elif char in CLOSING_BRACKETS: # Check if top of stack matches closing brackets
if s.is_empty(): # If stack is empty but we see a closing bracket
balanced = MORE_RIGHT
else:
top = s.pop()
# Get index of bracket at top of stack in OPEN_BRACKETS
index = 0
for i in range(len(OPEN_BRACKETS)):
if top == OPEN_BRACKETS[i]:
index = i
# Index of closing bracket should be same as open bracket
complimentary_bracket = CLOSING_BRACKETS[index]
if not char == complimentary_bracket:
balanced = MISMATCHED
char_index += 1
if not s.is_empty(): # If we still have opening brackets in the stack but we reach the end of the string
balanced = MORE_LEFT
return balanced
def stack_test(source):
"""
-------------------------------------------------------
Tests the methods of Stack for empty and
non-empty stacks using the data in source:
is_empty, push, pop, peek
(Testing pop and peek while empty throws exceptions)
Use: stack_test(source)
-------------------------------------------------------
Parameters:
source - list of data (list of ?)
Returns:
None
-------------------------------------------------------
"""
stack = Stack()
dummy = []
if stack.is_empty() == True:
print('Stack is empty.')
array_to_stack(stack, source)
print('Converting source into a stack...')
if stack.is_empty() == False:
print('source has been transferred into stack!')
print('\nPopping stack...')
while stack.is_empty() == False:
temp = stack.pop()
print(temp)
dummy.append(temp)
print('\nstack is empty. Pushing values back into stack...')
while dummy != []:
temp = dummy.pop()
print(temp)
stack.push(temp)
print('\nPushing complete! Peeking...')
print(stack.peek())
return
def stack_combine(source1, source2):
"""
-------------------------------------------------------
Combines two source stacks into a target stack.
When finished, the contents of source1 and source2 are interlaced
into target and source1 and source2 are empty.
Use: target = stack_combine(source1, source2)
-------------------------------------------------------
Parameters:
source1 - a stack (Stack)
source2 - another stack (Stack)
Returns:
target - the contents of the source1 and source2
are interlaced into target (Stack)
-------------------------------------------------------
"""
# Determine which stack is the shortest, going to loop over that
#shortest_stack = source2 if len(source1) > len(source2) else source1
shortest_stack = None
other_stack = None
if len(source1) > len(source2):
shortest_stack = source2
other_stack = source1
else:
shortest_stack = source1
other_stack = source2
target = Stack()
# Loop and append until shortest stack is empty
while not shortest_stack.is_empty():
val1 = shortest_stack.pop()
val2 = other_stack.pop()
target.push(val1)
target.push(val2)
# Handle the rest of the elements in the longer stack
for element in other_stack:
target.push(element)
return
def stack_test(source):
"""
-------------------------------------------------------
Tests the methods of Stack for empty and
non-empty stacks using the data in source:
is_empty, push, pop, peek
(Testing pop and peek while empty throws exceptions)
Use: stack_test(source)
-------------------------------------------------------
Parameters:
source - list of data (list of ?)
Returns:
None
-------------------------------------------------------
"""
s = Stack()
array_to_stack(s, source)
print(s.is_empty())
print(s.peek())
print(s.pop())
s.push(1)
return
def postfix(string):
"""
-------------------------------------------------------
Evaluates a postfix expression.
Use: answer = postfix(string)
-------------------------------------------------------
Parameters:
string - the postfix string to evaluate (str)
Returns:
answer - the result of evaluating string (float)
-------------------------------------------------------
"""
s = Stack()
expression = string.split(" ") # Split on spaces
for char in expression:
if char in OPERATORS:
# Order that we pop is important
operand2 = s.pop()
operand1 = s.pop()
if char == OPERATORS[0]: # Addition
value = operand1 + operand2
elif char == OPERATORS[1]: # Subtraction
value = operand1 - operand2
elif char == OPERATORS[-2]: # Multiplication
value = operand1 * operand2
elif char == OPERATORS[-1]: # Division, do not have to worry about division by zero
value = operand1 / operand2
s.push(value)
else: # Dealing with a numeric value
s.push(int(char))
answer = s.pop() # Answer should be the only thing left in the stack
return answer
def is_palindrome_stack(string):
"""
-------------------------------------------------------
Determines if string is a palindrome. Ignores case, spaces, and
punctuation in string.
Use: palindrome = is_palindrome_stack(string)
-------------------------------------------------------
Parameters:
string - a string (str)
Returns:
palindrome - True if string is a palindrome, False otherwise (bool)
-------------------------------------------------------
"""
r = 1
s_4 = Stack()
string1 = string
for x in ' ,.!?':
string1 = string1.replace(x, '')
string1 = string1.lower()
if (len(string1) % 2) == 0:
for x in string1:
if s_4.is_empty() == True:
s_4.push(x)
else:
y = s_4.pop()
if x != y:
s_4.push(y)
s_4.push(x)
else:
half = (len(string1) / 2) + 0.5
for x in string1:
if r < half:
s_4.push(x)
elif r > half:
y = s_4.pop()
if x != y:
s_4.push(y)
r += 1
if s_4.is_empty() == True:
palindrome = True
else:
palindrome = False
return palindrome
from Stack_array import Stack
values = [1, 2, 3, 4]
print("Values: {}".format(values))
s = Stack()
print(">> Is the stack empty?")
empty = s.is_empty()
print("Expect: {}\tGot: {}".format(True, empty))
print(">> Pushing values onto Stack")
for val in values:
s.push(val)
print("Stack contents: ", end='')
print("Expect: {}\tGot: ".format(values[::-1]), end='')
for elem in s:
print(elem, end=' ')
print()
print(">> Pop top of stack")
value = s.pop()
print("Expect: {}\tGot: {}".format(values[-1], value))
print(">> Peek the top of the stack")
peeked = s.peek()
print("Expect: {}\tGot: {}".format(values[-2], peeked))
Lab 2, Task 3 - utilities#stack_to_array ------------------------------------------------------------------------ Author: Nicolas Mills ID: 180856100 Email: [email protected] __updated__ = 2019-01-21 ------------------------------------------------------------------------ """ from utilities import stack_to_array from Stack_array import Stack target = [] array = [1, 2, 3, 4] s = Stack() for i in array: s.push(i) print("Array before: {}".format(target)) print("Stack before:") for i in s: print(i, end=' ') print() stack_to_array(s, target) print("Array after: {}".format(target)) print("Stack After:") for i in s: print(i, end=' ')