Day 18: Queues and Stacks

• Instructions:
  • Determine if a given string s is a palindrome (word, phrase, number, or other sequence of characters which reads the same backwards and forwards)
  • First take each character in s, enqueue it in a queue, and also push that same character onto a stack.
  • Then dequeue the first character from the queue and pop the top character off the stack, then compare the two characters to see if they are the same; as long as the characters match, we continue dequeueing, popping, and comparing each character until our containers are empty (a non-match means isn’t a palindrome).
  • Constraint:
    • s is composed of lowercase English letters.

Excercise

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import sys

class Solution:
    # Write your code here

# read the string s
s=input()
#Create the Solution class object
obj=Solution()   

l=len(s)
# push/enqueue all the characters of string s to stack
for i in range(l):
    obj.pushCharacter(s[i])
    obj.enqueueCharacter(s[i])
    
isPalindrome=True
'''
pop the top character from stack
dequeue the first character from queue
compare both the characters
''' 
for i in range(l // 2):
    if obj.popCharacter()!=obj.dequeueCharacter():
        isPalindrome=False
        break
#finally print whether string s is palindrome or not.
if isPalindrome:
    print("The word, "+s+", is a palindrome.")
else:
    print("The word, "+s+", is not a palindrome.")   

Solution

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import sys

class Solution:
    # Write your code here
    def __init__(self):
        self.stack = []
        self.queue = []
    
    def pushCharacter(self, char):
        self.stack.insert(0,char)
    
    def popCharacter(self):
        return self.stack.pop(0)
        
    def enqueueCharacter(self,char):
        self.queue.append(char)
        
    def dequeueCharacter(self):
        return self.queue.pop(0)
      
# read the string s
s=input()
#Create the Solution class object
obj=Solution()   

l=len(s)
# push/enqueue all the characters of string s to stack
for i in range(l):
    obj.pushCharacter(s[i])
    obj.enqueueCharacter(s[i])
    
isPalindrome=True
'''
pop the top character from stack
dequeue the first character from queue
compare both the characters
''' 
for i in range(l // 2):
    if obj.popCharacter()!=obj.dequeueCharacter():
        isPalindrome=False
        break
#finally print whether string s is palindrome or not.
if isPalindrome:
    print("The word, "+s+", is a palindrome.")
else:
    print("The word, "+s+", is not a palindrome.")