Python: Lowest Common Ancestor in a binary tree, challenge on CodeEval

Question

First of all, I know there are a lot of other threads dealing with this problem. What I want to know is why my solution doesn't seem to rank 100% when I submit it on CodeEval. It only ranks at 70%. When I test it on my local environment, it works just fine for all the test situations I've thrown at it.

I know my solution isn't the most efficient. What I tried to do is to come up with a solution on my own, one that I would understand. I will eventually compare it with others. But before that, can someone please explain what I'm doing wrong here?

class binary_tree(object):
def __init__(self, value=None, left=None, right=None):
    self.value=value
    self.left=left
    self.right=right

def insert(self, num):
    #print "...now:", num
    if self.value==num:
        return
    else:
        #print "descending from", self.value
        if num<self.value:
            if self.left:
                #print "descending to left"
                self.left.insert(num)
            else:
                #print "! found empty left"
                self.left=binary_tree(num)
        else:
            if self.right:
                #print "descending to right"
                self.right.insert(num)
            else:
                #print "! found empty right"
                self.right=binary_tree(num)

def tree_from_list(self, value, numbers):
    self.value=value
    for num in numbers:
        self.insert(num)

def __repr__(self,depth=0):
    rtn=""
    rtn+="\t"*depth+" "+str(self.value)+"\n"
    depth+=1
    if self.left:
        rtn+="\t"*depth+" left: "
        rtn+=self.left.__repr__(depth)
    if self.right:
        rtn+="\t"*depth+" right: "
        rtn+=self.right.__repr__(depth)
    return rtn


def find_parent_depth(self, num, depth=0):
    if self.left and self.left.value==num:
        #returns a list of two values, the first one being
        #the depth of the parent, and the second the value
        #itself. depth starts at 0, and increases as we descend
        return [depth, self.value]
    elif self.right and self.right.value==num:
        return [depth, self.value]
    else:
        depth+=1
        #checks for which path to descend on
        if num<self.value:
            if self.left:
                return self.left.find_parent_depth(num, depth)
            else:
                return self.value
        else:
            if self.right:
                return self.right.find_parent_depth(num, depth)
            else:
                return self.value

#lca = lowest common ancestor
def lca(self, v1, v2):  
    parent1=self.find_parent_depth(v1)
    parent2=self.find_parent_depth(v2)
    #checks for which parent has lower depth
    if parent1[0]<parent2[0]:
        #searches for ancestors till it reaches the same depth level
        while parent1[0]!=parent2[0]: 
            parent2=self.find_parent_depth(parent2[1])
        #checks if the ancestors coincide at that depth
        if parent1[1]==parent2[1]:
            #if they do, returns the parent value
            #THIS IS IT
            return parent1[1]
        #if it doesn't, we need to raise the level of the lowest one 
        #and do it all over again
        else:
            return self.lca(parent1[1], parent2[1])
    else:
        #searches for ancestors till it reaches the same depth level
        while parent2[0]!=parent1[0]: 
            parent1=self.find_parent_depth(parent1[1])
        #checks if the ancestors coincide at that depth
        if parent1[1]==parent2[1]:
            #if they do, returns the parent value
            #THIS IS IT
            return parent1[1]
        #if it doesn't, we need to raise the level of the lowest one 
        #and do it all over again
        else:
            return self.lca(parent2[1], parent1[1])
dis=binary_tree()
dis.tree_from_list(30, [8, 52, 3, 20, 10, 29, 12, 90, 89, 1])
print dis.lca(89, 12)

Answer 1

I had a similar problem. Given:

   30
   _|___
  |    |
  8   52
 _|___
 |   |
 3  20
    _|___
    |   |
   10   29

My hang up was related to LCA definition.

I found that the lowest common ancestor of 20 and 29 is 20, not 8 as I originally thought given the examples in the directions. Another example is LCA of 8 and 20 is 8.

After adjusting code my submission passed 100%.

Hope this helps. Cheers!