Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def minDepth(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if not root:
return 0
left = self.minDepth(root.left)
right = self.minDepth(root.right)
if not left and not right:
return 1
elif not left:
return right + 1
elif not right:
return left + 1
else:
return min(left, right) + 1