This one is interesting. It tricked me, I had answered the wrong question at first! It is curious how it defines the depth, that it requires a leaf node. I was computing something else, something like max height.

This one’s interesting because it provides a somewhat (unless if I’m missing something) complicated inductive case. Good to know!

class Solution(object):
    def minDepth(self, root):
        if root is None:
            return 0
        lDepth = self.minDepth(root.left)
        rDepth = self.minDepth(root.right)
        # Were we a leaf?
        if lDepth is 0 and rDepth is 0:
            return 1
        if lDepth is 0:
            return rDepth + 1
        if rDepth is 0:
            return lDepth + 1
        return min(lDepth, rDepth) + 1