find shortest path for steps with obstacles

[0] is for step 1 and [n-1] for step n.

    i: 01   n = 2, length = 2
 step: 12   
value:      x don't care

steps findBestPath(obstacles, steps):
    if obstacles == null || obstacles.length() == 0:
        throw
    if steps.any(step <= 0):
        throw
    sortDesc(steps)
    best = new
    findBestPath(obstacles, steps, best)
    return best

findBestPath(obstacles, steps, best, i = a.length()):
    if i == 0:
        return true
    if hasObstacle(obstacles, i):
        return false
    for step in steps:
        best.add(step)
        if findBestPath(obstacles, steps, best, i -step):
            return true
        best.removeLast(step)
    return false

bool hasObstacle(obstacles, i):
    if !(1 <= i <= a.length()):
        return false
    return obstacles[i-1]