function findMax(val) {
  const arr = val.split('');
  const reg = /\d+/g;
  const max = Math.max.apply(Math, val.match(reg));
  console.log(max);
}

function main() {
  for (let i = 0; i < size; i++) {
    const b = a.concat();
    b.splice(b.indexOf(a[i]), 1);
    pailie(a[i], b);
  }
}

function pailie(head, tail) {
  for (let i = 0; i < tail.length; i++) {
    if (tail.length === 1) {
      console.log(head +''+ tail[0]);
    } else {
      const b = tail.concat();
      b.splice(b.indexOf(tail[i]), 1);
      pailie(head+''+tail[i], b);
    }
  }
}

	

第二题通过33%，惨的不谈