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Challenge: Reverse String Using Linked List

Instructions

Write a function called reverseStringLinkedList that takes in a string and returns the reverse of that string.

The function should return the reversed string, but I want you to use the LinkedList class to do it.

Function Signature

/**
 * Returns the reverse of a string.
 * @param {string} str - The string to reverse.
 * @returns {string} - The reverse of the string.
 */
function reverseStringLinkedList(str: string): string;

Examples

reverseStringQueue('hello'); // olleh
reverseStringQueue('Howdy'); // ydwoH
reverseStringQueue('Greetings from Earth'); // htraE morf sgniteerG

Hints

• Loop through the string and add each character to the linked list.
• Loop through the linked list and build the reversed string.

Solutions

Click For Solution

function reverseStringLinkedList(str) {
  const list = new LinkedList();

  for (let i = str.length - 1; i >= 0; i--) {
    list.add(str[i]);
  }

  let reversedString = '';
  let current = list.head;

  while (current !== null) {
    reversedString += current.data;
    current = current.next;
  }

  return reversedString;
}

Explanation

• Initialize a new LinkedList instance.
• Iterate through the string and add each character to the linked list.
• Initialize a variable called reversedString and set it to an empty string and a variable called current and set it to the head of the linked list.
• Iterate through the linked list and build the reversed string by adding each node's data to the reversedString variable and then setting current to the next node.
• Return the reversedString variable.

Test Cases

test('Reversing a string', () => {
  expect(reverseStringLinkedList('Hello')).toBe('olleH');
  expect(reverseStringLinkedList('JavaScript')).toBe('tpircSavaJ');
  expect(reverseStringLinkedList('12345')).toBe('54321');
});