Reverse

The reverse algorithm takes an array of values and returns the values in reverse order. It works by iterating over the array and swapping the first and last values, then the second and second-to-last values, and so on until the middle of the array is reached.

Source Code Listing

code.ts

/**
 * @file Reverse
 * @author Dustin Boston
 * @see Cormen, T, Leiserson, C, Rivest, R, and Stein, C. (2001).
 *   Introduction to Algorithms. (2nd ed). The MIT Press.
 */

/**
 * Reverses the order of elements in the provided array.
 *
 * @param arrayToReverse - The array to be reversed.
 * @returns The provided array with its elements reversed.
 */
export function reverse<ValueType extends string[] | number[]>(
  arrayToReverse: ValueType,
) {
  const length = arrayToReverse.length;

  // Swap characters from start and end of string progressing inward
  for (
    let headIndex = 0, tailIndex = length - 1;
    headIndex < tailIndex;
    headIndex++, tailIndex--
  ) {
    const temporary = arrayToReverse[headIndex];
    arrayToReverse[headIndex] = arrayToReverse[tailIndex];
    arrayToReverse[tailIndex] = temporary;
  }

  return arrayToReverse;
}

// Usage
(() => {
  const wordToReverse = "reverse";
  const arrayToReverse = wordToReverse.split("");
  const actual = reverse(arrayToReverse).join("");
  const expected = "esrever";

  if (actual !== expected) {
    throw new Error(`Expected ${expected} but got ${actual}`);
  }

  console.log(`'${wordToReverse}' reversed to '${actual}'`);
})();