Question

I have an unusual tree array like this:

[[0, 1], [1, 2], [2, 3], [2, 4], [2, 5], [5, 6], 
 [4, 6], [3, 6], [0, 7], [7, 6], [8, 9], [9, 6]]

Each element of the array is a pair, which means second one is a follower of the first, e.g.:

[0, 1] - 0 is followed by 1
[1, 2] - 1 is followed by 2

I am trying to extract array like this:

0 1 2 3 6    
0 1 2 4 6    
0 1 2 5 6
0 7 6
8 9 6

I couldn’t code a robust traversal to extract all possible paths like this. How can I do it with Python?

Answer 1

Here you go. Not the nicest code on earth but it works:

inputValues = [[0, 1], [1, 2], [2, 3], [2, 4], [2, 5], [5, 6], [4, 6], [3, 6], [0, 7], [7, 6], [8, 9], [9, 6]]

tree = {}
numberOfChildren = {}
for (f, t) in inputValues:
  if not tree.has_key(f):
    tree[f] = []
  tree[f].append(t)
  if not numberOfChildren.has_key(t):
    numberOfChildren[t] = 0
  numberOfChildren[t] += 1

roots = [c for c in tree if c not in numberOfChildren]
permutations = []

def findPermutations(node, currentList):
  global tree
  global permutations
  if not tree.has_key(node):
    permutations.append(currentList)
    return
  for child in tree[node]:
    l = list()
    l.extend(currentList)
    l.append(child)
    findPermutations(child, l)

for r in roots:
  findPermutations(r, [r])

print permutations