二叉树层次遍历下到上，左到右python

Posted 2021-03-06 limingqi

# 利用队列进行层次遍历就行
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
class Solution:

    def Print(self, pRoot):

        if not pRoot:
            return []
        queue = [pRoot]
        outList = []
        while queue:
            res = []
            nextQueue = []
            for point in queue:  # 这里再遍历每一层
                res.append(point.val)
                if point.left:
                    nextQueue.append(point.left)
                if point.right:
                    nextQueue.append(point.right)
            outList.append(res)
            queue = nextQueue   #覆盖的作用
        return outList[::-1]


t = TreeNode(0)
t.left = TreeNode(1)
t.right = TreeNode(2)
t.left.left = TreeNode(3)
t.left.right = TreeNode(6)
t.right.left = TreeNode(7)

s=Solution()
print(s.Print(t))