DATA STRUCTURES IN PYTHON3

STACKS 

REMOVE ADJACENT DUPLICATES USING STACKS

import string as s
stk=[]
n=input("Enter the characters")
for char in n:
	if len(stk)==0 and  char in s.ascii_lowercase:
		stk.append(char)
	elif char in s.ascii_lowercase and stk[-1]==char:
		stk.pop()
	elif char in s.ascii_lowercase and stk[-1]!=char:
		stk.append(char)
print("characters with all adjacent duplicates removed are ")
print(''.join(stk))


POSTFIX EVALUATION USING A STACK


stk=[]
n=input('Enter the required postfix expression')
for char in n:
	if char.isdigit():
		stk.append(char)
	else:
		if char=='+':
			m=stk.pop()
			n=stk.pop()
			stk.append(str(int(m)+int(n)))

		elif char=='-':
			m=stk.pop()
			n=stk.pop()
			stk.append(str(abs(int(m)-int(n))))

		elif char=='*':
			m=stk.pop()
			n=stk.pop()
			stk.append(str(int(m)*int(n)))

		elif char=='/':
			m=stk.pop()
			n=stk.pop()
			if int(m)>int(n):
				stk.append(str(int(m)//int(n)))
			else:
				stk.append(str(int(n)//int(m)))

print("The value of the above postfix expression is");
print(int(stk[0]))

BALANCING PARENTHESIS USING STACKS


stk=[]
def push(k):
	stk.append(k)
def popped():
	if isEmpty():
		return 0
	else:
		return stk.pop()
def check(b,r):
	if b==')'and r=='(':
		print('checked')
	if b==']' and r=='[':
		print('checked')
	if b=='}' and r=='{':
		print('checked')

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


n=input("Enter the string to check the required parenthesis")
count=0
m=1
for i in n:
	count+=1
	if i in '{([':
		push(i)
	if i in ')}]':
		m=popped()
		if m==0:
			print('Stack underflow')
			break
		else:
			check(i,m)
if m is not 0:


	if isEmpty():
		print('Balanced Parenthesis')
	else:
		print('Unbalanced')

# ** if stack underflow occurs then still its unbalanced