Brute force solution to level 47 in Black, by Bart Bonte.

black47.py

numbers = [4, 6, 1, 3, 4, 4, 5, 3, 2, 3, 5, 2, 2, 4, 2, 6]
size = len(numbers)

path = []

def explore(pos):
    num = numbers[pos]

    print('explore', pos, num)

    if pos in path:
        print('already visited')
        return False
    else:
        path.append(pos)

    print()
    print(''.join( ('X' if pos in path else 'O') for pos in range(size) ))
    print('[ ', end='')
    for pos in path:
        print(pos, numbers[pos], end=' | ')
    print()
    print()

    if len(path) >= size:
        print('done')
        return True

    num = numbers[pos]
    right = (pos + num) % size
    left = (pos - num) % size

    if explore(right):
        return True

    if explore(left):
        return True

    print('back out')
    path.pop()
    return False


for start in range(size):
    if explore(start):
        break

for pos in path:
    print(pos, numbers[pos])