513. Find Bottom Left Tree Value

Given a binary tree, find the leftmost value in the last row of the tree.

Input:

        1
       / \
      2   3
     /   / \
    4   5   6
       /
      7

Output:
7

广度优先搜索问题，对每层遍历得到每层的数字，输出第一个数字

# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
···
class Solution(object):
    def findBottomLeftValue(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        Node = [root]
        tmp = []
        result = root.val
        while len(Node):
            tmp = []
            for i in Node:
                if i.left:
                    tmp.append(i.left)
                if i.right:
                    tmp.append(i.right)
            Node = tmp
            if len(Node):
                result = Node[0].val
        return result