Good afternoon! Here's our prompt for today.

Reversing Only Alphabetical Characters in a String

The Problem Statement

You are provided with a string that's a blend of alphabetic and non-alphabetic characters. Think of a beach where you find both shells (a-Z) and other things like plastic wrappers or dollar bills ($, !, etc.). For example, you might get:

1'sea!$hells3'

Your mission, should you choose to accept it, is to flip only the alphabetical shells while keeping the other items ($, !, etc.) in their original positions.

For example, when calling:

1reverseOnlyAlphabetical('sea!$hells3');

You should expect the output to be:

1'sll!$ehaes3'

Constraints to Consider

• String Length: The length of the given string is up to 100,000 characters.
• Character Set: You'll be working with ASCII characters.
• Time Complexity: Aim for a time complexity of O(n).
• Space Complexity: Aim for a space complexity of O(n).

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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var assert = require('assert');

​

function reverseOnlyAlphabetical(str) {

  return str;

}

​

try {

  assertIsFunction(

    reverseOnlyAlphabetical,

    'reverseOnlyAlphabetical is a function'

  );

​

  console.log('PASSED: ' + 'Expect `reverseOnlyAlphabetical` is a function');

} catch (err) {

  console.log(err);

}

​

try {

  assert.equal(

    reverseOnlyAlphabetical('sea!$hells3'),

    'sll!$ehaes3',

    "reverseOnlyAlphabetical('sea!$hells3') should equal 'sll!$ehaes3'"

  );

​

  console.log(

    'PASSED: ' +

      "Expect `reverseOnlyAlphabetical('sea!$hells3')` to return `'sll!$ehaes3'`"

  );

} catch (err) {

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Here's how we would solve this problem...

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