How to make this recursive function iterative in python?

Question

Usually I'm good with this type of thing, but this is bugging me. I had to write this function last week, and writing it recursively made the most sense, although now I'm trying to find a way to make it iterative to incorporate it into another function I'm writing. This is the recursive version of the function,

def XXX (x,y,z):
    if z[x][0][0] != z[y][0][0]:
        XXX(z[x][0],z[y][0],z)
    else:
        return z[x][0]

and this is the data structure

{'A': [('AD', 4.0), None, None], 'C': [('ADBFGC', 14.5), None, None], 'B': [('BF', 0.5), None, None], 'E': [('ADBFGCE', 17.0), None, None], 'D': [('AD', 4.0), None, None], 'G': [('BFG', 6.25), None, None], 'F': [('BF', 0.5), None, None], 'ADBFG': [('ADBFGC', 6.25), ('AD', 4.25), ('BFG', 2.0)], 'BF': [('BFG', 5.75), ('B', 0.5), ('F', 0.5)], 'ADBFGC': [('ADBFGCE', 2.5), ('ADBFG', 6.25), ('C', 14.5)], 'ADBFGCE': [None, ('ADBFGC', 2.5), ('E', 17.0)], 'BFG': [('ADBFG', 2.0), ('BF', 5.75), ('G', 6.25)], 'AD': [('ADBFG', 4.25), ('A', 4.0), ('D', 4.0)]}

I'm completely blanking on this, any help would be appreciated :)

Answer 1

def ClosestCommonAncestor(otu1, otu2, tree):
    while tree[otu1][0][0] != tree[otu2][0][0]:
        otu1,otu2,tree = tree[otu1][0],tree[otu2][0],tree
    return tree[otu1][0]

Do note that it should be possible to add functionality to the recursive version. I would also suggest defining a Tree(*children) class to make things clearer.

Answer 2

def ClosestCommonAncestor (otu1,otu2,tree):
    while True:
        a = tree[otu1][0]
        b = tree[otu2][0]
        if a[0] == b[0]:
            return a
        otu1 = a
        otu2 = b