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Data Structures and Algorithms in Python

Is Palindrome

Explore methods to determine if a string is a palindrome in Python. Learn a straightforward solution using extra space and a preferred approach using constant space and linear time. Understand handling alphanumeric characters and case insensitivity to validate palindromes effectively.

We'll cover the following...

In this lesson, we will be considering how to test whether a string is a palindrome in Python. At first, we’ll come up with a concise solution that takes extra space, but we’ll eventually code a solution that takes a linear amount of time and a constant amount of space.

A palindrome is a word, number, phrase, or any other sequence of characters that reads the same forward as it does backward.

Here are some examples of a palindrome:

Implementation

Let’s get started with the implementations.

Solution 1

Python 3.5
s = "Was it a cat I saw?"
# Solution uses extra space proportional to size of string "s"
s = ''.join([i for i in s if i.isalnum()]).replace(" ", "").lower()
print(s == s[::-1])

Let’s discuss the above one-line solution in parts. So the [i for i in s if i.isalnum()] statement returns ...