Alphabet Spiral- PhillyDev Slack #daily_programmer - 20180222

dp20180222.js

let getSideSize = function(size) {
  if (size < 1) {
    return 0;
  } else if (size == 1) {
    return 2;
  } else {
    return size + getSideSize(size - 1);
  }
};

let fillSpiral = function(level, startLetter, spiral) {
  let side = getSideSize(level);
  let length = (side - 1) * 4;

  let i = startLetter;
  let x = 0;
  let y = 0;

  let direction = [0, 1, 0, -1];
  let dX = 0;
  let dY = 1;

  for (let i = 0; i < 4; i++) {
    for (let j = 0; j < side; j++) {
      if (spiral[x][y] == ' ') {
        spiral[x][y] = String.fromCharCode(65 + startLetter++);
      }
      x += direction[dX];
      y += direction[dY];
      startLetter %= 26;
    }
    // Back up the last position move
    x -= direction[dX];
    y -= direction[dY];
    dX = ++dX % 4;
    dY = ++dY % 4;
  }
  return [startLetter, spiral];
};

let alphabetSpiral = function(size) {
  let spiralLength = getSideSize(size);
  let spiral = new Array(spiralLength)
    .fill(0)
    .map(v => new Array(spiralLength).fill(' '));
  let startLetter = 0;

  for (let i = 1; i <= size; i++) {
    [startLetter, spiral] = fillSpiral(i, startLetter, spiral);
  }

  return spiral.map(v => v.join('')).join('\n');
};

let test = 3;
let result = alphabetSpiral(3);
console.log(result);