여친 기다리다ㅠ심심해셔 ㅇㅅ틀린거 있음 지적좀
function dalpaeng(length) {
  let result = [];
  let x, y, num;
  x = y = num = 0;
  x--;
  let direction = 1;
  while(1) {
     for (let i = 0; i < length ; i++) {
       x += direction;
       result[y][x] = ++num;
     }
     length--;
     if (length === 0) break;
     for (let i = 0; i < length ; i++) {
        y += direction;
        result[y][x] = ++num;
     }
     direction *= -1;
  }
  return result;
}