Keyboard spell test

keyboardSpell.test.readme.md

Keyboard spell test

Write a function spell() that takes a keyboard layout as a 2D array and an input string. The function will output a list of instructions that will traverse the keyboard to print the input string.

The instructions are:

• U: up
• D: down
• L: left
• R: right
• P: print character

Assume the starting key is the first element in the first row (q in the example below) E.g.

spell(
  [
    ['q','w','e','r','t','y','u','i','o','p'],
    ['a','s','d','f','g','h','j','k','l'],
    ['z','x','c','v','b','n','m']
  ],
  "hello"
);

Should output: DRRRRRPULLLPDRRRRRRPPUP

solution.js

/*
Write a function spell() that takes a keyboard layout as a 2D array and an input string. The function will output a list of instructions that will traverse the keyboard to print the input the string.

The instructions are up, down, left, right and print. i.e. U, D, L, R and P

Assume the starting key is the first element in the first row ('q' in the example below) e.g.

spell(
  [
    ['q','w','e','r','t','y','u','i','o','p'],
    ['a','s','d','f','g','h','j','k','l'],
    ['z','x','c','v','b','n','m']
  ],
  "hello"
);

Should output: "DRRRRRPULLLPDRRRRRRPPUP"
*/

/**
 * Generates instructions to spell a given string on a provided keyboard layout.
 * @param {Array} layout - The keyboard layout as a 2D array.
 * @param {string} s - The string to spell on the keyboard.
 * @returns {string} - The instructions to spell the string on the keyboard.
 */
function spell(layout, s) {
  /*
    Remap keyboard layout to unique character codes
    [
      ['q','w','e','r','t','y','u','i','o','p'],
      ['a','s','d','f','g','h','j','k','l'],
      ['z','x','c','v','b','n','m']
    ]
    =>
    [
      [0,1,2,...,9],
      [10,11,...,18],
      [19,20,...,25]
    ]
  */
  let charI = 0;
  const charMap = {};
  const rowSets = [];

  const charLayout = layout.map((row) => {
    const mappedRow = row.map((char) => {
      charMap[char] = charI;
      return charI++;
    });
    rowSets.push(new Set(mappedRow));
    return mappedRow;
  });

  let curRowIndex = 0;
  let curColIndex = 0;
  let seq = '';

  // for each given character
  for (let sIndex = 0; sIndex < s.length; sIndex++) {
    const charCode = charMap[s.charAt(sIndex)];

    // find row
    const targetRowIndex = rowSets.findIndex((rowSet) => rowSet.has(charCode));
    if (targetRowIndex === -1) {
      throw new Error(`Character "${s.charAt(sIndex)}" not found in layout`);
    }
    seq += new Array(Math.abs(targetRowIndex - curRowIndex))
      .fill(targetRowIndex - curRowIndex > 0 ? 'D' : 'U')
      .join('');
    curRowIndex = targetRowIndex;

    // find col
    const curCode = charLayout[curRowIndex]?.[curColIndex];
    if (curCode == undefined) {
      throw new Error(`Invalid current position at row ${curRowIndex}, col ${curColIndex}`);
    }
    const colDistance = Math.abs(charCode - curCode);
    seq += new Array(colDistance).fill(charCode - curCode > 0 ? 'R' : 'L').join('');
    curColIndex += colDistance * (charCode - curCode > 0 ? 1 : -1);

    seq += 'P';
    // request char print
  }

  // console.log('seq = ', seq);
  return seq;
  // solution: 'DRRRRRPULLLPDRRRRRRPPUP';
}

// UNIT TESTS
console.assert(
  spell(
    [
      ['q', 'w', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p'],
      ['a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l'],
      ['z', 'x', 'c', 'v', 'b', 'n', 'm'],
    ],
    'hello'
  ) === 'DRRRRRPULLLPDRRRRRRPPUP',
  'Failed unit test'
);