In this article, we use python 3.8 to create our own stack structure with basic functionality, which has only three functions: push, pop, and peek.
` #!/usr/bin/env python
# * coding: utf-8 *
# @Time : 2024/9/15 19:26
# @Author : Huzhaojun
# @Version：V 1.0
# @File :
# @desc :
# Data Structures Review Chapter 1, Implementation and Use of Stack Structures #
class Node.
"""Creating a node""""
def __init__(self, data=None).
= data
= None
class stack.
def __init__(self).
self._n = 0 # Record the number of elements. self._n = None # This is a pointer to the top of the stack.
= None # This is a pointer to the top of the stack forever.
= None # Point to the next element
def push(self, data): # push pressed into function
node = Node(data) # create a new node and add it to the stack
if : # If there is an element on the stack, update the top pointer to point to it.
=
= node
else: # Otherwise point directly to the new node
= node
self._n += 1
def pop(self): # pop pop function
if : # Determine if an element exists on top of the stack, if it does, do the next step, otherwise return None.
data = # Get the value at the top of the stack.
self._n -= 1
if : # If there is another element under the top of the stack, replace the value of the pointer.
data = # Get the value of the top of the stack.
else: # Otherwise define it as None
= None
return data
return None
def peek(self): # Look at the top of the stack.
if :
return
return None
`
Usage Process:
x = stack()
(1)
(2)
print(())
print(())
print(())
Output results:
2
2
1
Let's go to war.
The bracket-matching application is a common validation program for matching brackets, including (), {}, [] symbols are balanced, and the number of left and right brackets matches, it will also make sure that one pair of brackets is actually contained in another pair of brackets.
Let's try to validate an xml file and see how it turns out, notice that I added a new __len__ function to the stack:
`
#!/usr/bin/env python
# * coding: utf-8 *
# @Time : 2024/9/15 19:26
# @Author : Huzhaojun
# @Version：V 1.0
# @File :
# @desc :
# Data Structures Review Chapter 1, Implementation and Use of Stack Structures #
class Node.
"""Creating a node""""
def __init__(self, data=None).
= data
= None
class stack.
def __init__(self).
self._n = 0 # Record the number of elements. self._n = None # This is a pointer to the top of the stack.
= None # This is a pointer to the top of the stack forever.
= None # Point to the next element
def __len__(self): # Define the len event.
return self._n
def push(self, data): # push pressed into function
node = Node(data) # create a new node and add it to the stack
if : # Update the top pointer if there is an element on the stack.
=
= node
else: # Otherwise point directly to the new node
= node
self._n += 1
def pop(self): # pop pop function
if : # Determine if an element exists on the top of the stack, if it does, do the next step, otherwise return None.
data = # Get the value at the top of the stack.
self._n -= 1
if : # If there is another element under the top of the stack, replace the value of the pointer.
data = # Get the value of the top of the stack.
else: # Otherwise define it as None
= None
return data
return None
def peek(self): # Look at the top of the stack.
if :
return
return None
def check_brackets(statement):
Stack = stack()
for ch in statement: if ch in "({[<":)
if ch in "({[<".
(ch)
if ch in ")}]>":
last = ()
if last + ch in ("()", "[]", "{}", "<>").
()
else.
return False
if len(Stack) > 0.
return False
return True
text = """
<?xml version="1.0" encoding="UTF-8"? >?
<ui version="4.0" >
<class>MainWindos</class>
<widget class="QDialog" name="MainWindos"> <property name="MainWindos"> <class>/class>
<property name="geometry"> <rect>.
<rect>.
<x>0</x>
<y>0</y>
<width>402</width> <height> <height> <height>
<height>575</height>
</rect>.
</property>.
<property name="windowTitle"> </property> </property>
<string>music</string> </string>
</property>
</widget>.
</property> </widget> <resources/>
</widget> <resources/> </connections/>.
</ui>"""
print(check_brackets(text))
`
Run results:
True
Self-built data structures can be added to the needs of any desired method of implementation, although the built-in methods can already solve most of the problems, but we can learn more in the process.OVER