leetcode 513

这题的思想很简单，就是利用递归。这里可以利用python可以返回多个值的性质，我们可以在递归的过程中返回深度和最左边的值，然后判断两边哪一边更深，将更深的值和深度返回到上一层，最后就能够得到结果。附代码：

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def findBottomLeftValue(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        def recursive(root):
            if root.left == None and root.right == None:
                return 1,root.val
            elif root.right == None:
                temp_depth,temp_val = recursive(root.left)
                return temp_depth+1,temp_val
            elif root.left == None:
                temp_depth,temp_val = recursive(root.right)
                return temp_depth+1,temp_val
            left_depth,left_val = recursive(root.left)
            right_depth,right_val = recursive(root.right)
            
            if left_depth >= right_depth:
                return left_depth+1, left_val
            else:
                return right_depth+1, right_val
        depth,val = recursive(root)
        return val