A Common-Sense Guide to Data Structures and Algorithms, Second Edition, 2nd Edition

Word Builder

The next example is an algorithm that collects every combination of two-character strings built from an array of single characters. For example, given the array: ["a", "b", "c", "d"], we’d return a new array containing the following string combinations:

[
  'ab', 'ac', 'ad', 'ba', 'bc', 'bd',
  'ca', 'cb', 'cd', 'da', 'db', 'dc'
]

Following is a JavaScript implementation of this algorithm. Let’s see if we can figure out its Big O efficiency:

function wordBuilder(array) {
  let collection = [];

  for(let i = 0; i < array.length; i++) {
    for(let j = 0; j < array.length; j++) {
      if (i !== j) {
        collection.push(array[i] + array[j]);
      }
    }
  }

  return collection;
}

Here we’re running ...