Interview question

/*
 *  test cases
 * 
 *  case 1.
 * 
 *  #============#
 *  #===#====#===#
 *  #==##==#######
 *  #=############
 *  #=############
 * ---------------
 * [5,0,2,3,4,2,2,3,3,4,3,3,3,5] => 12 + 10 + 4 + 1 + 1 = 28
 * 
 * 
 *  case 2.
 *   
 *   #=======#
 *  ##=======#===#
 *  ##=##==#=#####
 *  ########=#####
 *  ##############
 * ---------------
 * [4,5,2,3,3,2,2,3,1,5,3,3,3,4] => 7 + 10 + 4 + 1 = 22
 * 
 */


function min (a, b) {
  if (a > b) {
    return b;
  }
  else {
    return a;
  }
}


function fillout (blocks, from, to) {

  from = from || 0;
  to   = to || blocks.length - 1;

  if (to < from + 2) {
    return 0;
  }

  var nblocks = 0;;

  var bFrom = blocks[from]
    , bTo   = blocks[to]
    , bSurf = min(bFrom, bTo);

  for (var i = 1; i < (to - from + 1); i++) {
    if (blocks[from + i] > bSurf) {
      nblocks = fillout(blocks, from, from + i) + fillout(blocks, from + i, to);
      break;
    }
    else {
      nblocks += (bSurf - blocks[from + i]);
    }
  }

  return nblocks;
}


var assert = require('assert');

assert(0 === fillout([1, 3]));

assert(1 === fillout([1, 0, 1]));
assert(2 === fillout([3, 0, 2]));

assert(28 === fillout([5,0,2,3,4,2,2,3,3,4,3,3,3,5]));
assert(22 === fillout([4,5,2,3,3,2,2,3,1,5,3,3,3,4]));