Question

Imagine I had a function called multi0(Array) and I wanted it to take an Array as an argument.

If I did multi0([5]), it would return an array that looks like

[0,0,0,0,0]

If I did multi0([5,3]), it would return an array that looks like

[
    [0,0,0],
    [0,0,0],
    [0,0,0],
    [0,0,0],
    [0,0,0]
]

I attempted this with recursion, but it didn’t work. How do you implement this?

Answer 1

Like this:

function multi0(arr) {
  if (arr.length == 0) {
    return 0;
  } else {
    var children = arr.slice(1);
    var result = [];
    for (var i = 0; i < arr[0]; i++) {
      result.push(multi0(children));
    }
    return result;
  }
}

http://jsfiddle.net/ffuH4/

Or the slightly longer but more effective:

function multi0(arr) {
  var result = [];
  if (arr.length == 1) {
    for (var i = 0; i < arr[0]; i++) {
      result.push(0);
    }
  } else {
    var children = arr.slice(1);
    for (var i = 0; i < arr[0]; i++) {
      result.push(multi0(children));
    }
  }
  return result;
}