513. Find Bottom Left Tree Value 二叉树左下节点的值

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

Example 1:

Input:

    2
   / 
  1   3

Output:
1

Example 2: 

Input:

        1
       / 
      2   3
     /   / 
    4   5   6
       /
      7

Output:
7

Note: You may assume the tree (i.e., the given root node) is not NULL.

求二叉树左下方节点的值，使用广度优先遍历，每遍历一层刷新result值

class Solution(object):
    def findBottomLeftValue(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        left = 0
        if(not root):
            return left
        result = []
        queue = [root]
        while(queue):
            count = len(queue)
            for i in range(0, count):
                node = queue.pop(0)
                if i == 0:
                    left = node.val
                if(node.left):
                    queue.append(node.left)
                if(node.right):
                    queue.append(node.right)
        return left

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