Spiral Array

spiralarray.js

function createSpiral(dimension) {

  console.time();
  
  // square array generator
  const matrix = (dimension) => {
    return new Array(dimension).fill(0).map((obj, idx) => {
      return obj[idx] = new Array(dimension).fill(0);
    });
  }

  let square = matrix(dimension);
  let x,y;

  // fill in top/bot edges with 1, concentrically
  x = 0;
  y = dimension;
  while(x < y) {
    square[x].fill(1,x,y);
    square[y-1].fill(1,x,y);
    // fill in left/right edges with 1, concentrically
    for(let i = x; i < y; i++) {
      square[i][x] = 1;
      square[i][y-1] = 1;
    }
    x+=2;
    y-=2;
  }

  // diagonal XOR that bitflips from top-left to center-center
  x = 0;
  y = 0;
            // if a 2x2 square is possible, round the upper bound downward to prevent it
  let wtf = (dimension % 4 == 0) ? Math.floor((dimension-1)/2) : Math.ceil((dimension-1)/2);
  while(x < wtf) {
    x++;
    square[x][y] ^= 1;
    y++;
    continue;
  }

  console.timeEnd();
  console.log(`\nGenerating spiral array of size ${dimension}`);
  console.log(square);
  console.log(`\n`);

}



/* IGNORE EVERYTHING BELOW THIS LINE */

const readline = require('readline');
let rl = readline.createInterface(process.stdin, process.stdout);

console.log("Spiral Array Generator. Enter a number, or enter 0 to quit.\n");
rl.prompt();

rl.on('line', (line) => {
  if (/^\d+$/.test(line.trim())) {
    switch(line.trim()) {
      case '0':
          rl.close();
          break;
      default:
          createSpiral(Number(line.trim()));
      break;
    }
  } else {
    console.log("Bad input. Try again.");
  }
}).on('close', () => {
    console.log("Have a nice day!");
    process.exit(0);
});