‘Is It Palindrome?’ Reimagined: Algorithm Patterns in 5 Languages

Palindrome checking is a timeless programming exercise—simple enough to grasp quickly, yet rich enough to explore a multitude of patterns, language intricacies, and optimization strategies. In this article, we’ll reimagine the common ‘Is it a palindrome?’ algorithm by implementing it in five very different languages: Python, JavaScript, Java, Bash, and SQL. Along the way, we’ll demonstrate how the same logic is expressed differently—and share tips for writing efficient, idiomatic code in each.

1. What Is a Palindrome?

A palindrome is a string that reads the same forward and backward. Examples include "madam", "racecar", and "121". To check whether a string is a palindrome, we need to compare characters from both ends, moving toward the center.

In all implementations, we’ll:

Normalize the string (strip spaces, make lowercase)
Compare the string to its reverse

This common high-level logic is applicable across all programming environments, making it a great case study in algorithmic translation.

2. Python: Concise and Readable

Python’s rich string manipulation features make it a go-to for quick scripting tasks. Here’s a straightforward implementation:

def is_palindrome(s):
    s = ''.join(filter(str.isalnum, s)).lower()  # remove non-alphanumeric, lowercase
    return s == s[::-1]  # compare to reversed string

print(is_palindrome("A man, a plan, a canal: Panama"))  # True

Why it works: Filtering removes punctuation/whitespace, the slice s[::-1] reverses the string efficiently using Python slicing.

Tip: For long strings, consider using two-pointer technique instead of reversing the string, to save memory.

3. JavaScript: Lightweight and Ubiquitous

JavaScript shines on the frontend, but also works well in Node.js scripts. Here’s the algorithm in idiomatic JS:

function isPalindrome(str) {
    str = str.replace(/[^a-zA-Z0-9]/g, '').toLowerCase();
    return str === str.split('').reverse().join('');
}

console.log(isPalindrome("A man, a plan, a canal: Panama")); // true

Why it works: RegExp cleans the string. JS arrays support reverse() which simplifies logic by converting the string to an array, reversing and rejoining it.

Tip: Be mindful of Unicode characters when dealing with multilingual datasets.

4. Java: Verbose But Explicit

Java requires more boilerplate but it offers type safety and clearer control flow:

public class PalindromeChecker {
    public static boolean isPalindrome(String input) {
        StringBuilder sb = new StringBuilder();
        for (char c : input.toCharArray()) {
            if (Character.isLetterOrDigit(c)) {
                sb.append(Character.toLowerCase(c));
            }
        }
        String cleaned = sb.toString();
        String reversed = new StringBuilder(cleaned).reverse().toString();
        return cleaned.equals(reversed);
    }

    public static void main(String[] args) {
        System.out.println(isPalindrome("A man, a plan, a canal: Panama")); // true
    }
}

Why it works: Uses StringBuilder to construct filtered string and reverse it. Java’s type enforcement prevents surprises in edge cases.

Tip: For large-scale processing, consider using char[] arrays for lower overhead.

5. Bash: Minimalism Meets Text Processing

While not ideal for complex processing, Bash shines in automation tasks and small validation scripts. Here’s a compact palindrome check using CLI tools:

#!/bin/bash

is_palindrome() {
  input=$(echo "$1" | tr -cd '[:alnum:]' | tr '[:upper:]' '[:lower:]')
  reverse=$(echo "$input" | rev)
  [[ "$input" == "$reverse" ]] && echo "true" || echo "false"
}

is_palindrome "A man, a plan, a canal: Panama"

Why it works: tr cleans the string; rev reverses text. Comparison uses Bash pattern matching.

Tip: Use shell scripts for lightweight validation in pipelines, such as CI/CD tools or cron jobs.

6. SQL: Declarative Logic for Set-Based Thinking

SQL is not designed for string manipulation as naturally as procedural languages, but we can still perform a palindrome check. Here’s an example using PostgreSQL:

WITH cleaned AS (
  SELECT lower(regexp_replace('A man, a plan, a canal: Panama', '[^a-zA-Z0-9]', '', 'g')) AS val
), reversed AS (
  SELECT val, reverse(val) AS rev_val FROM cleaned
)
SELECT val = rev_val AS is_palindrome FROM reversed;

Why it works: The regexp_replace function strips non-alphanumerics, and reverse() performs the comparison.

Tip: Use this query to validate text columns in bulk across database rows. Indexing cleaned values can drastically improve performance for large datasets.

Conclusion: Patterns Over Syntax

As we’ve seen, the core palindrome algorithm remains functionally the same across these diverse environments. The primary differences lie in syntax, paradigms (functional vs. procedural), and idiomatic approaches. Understanding language strengths and tradeoffs helps build better abstractions and select the right tool for the job.

Palindrome checking may be simple, but reimagining it across languages is a great exercise for learning, refactoring, and thinking in patterns. Try implementing it in another language you know—or even better, one you don’t!

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