leetcode 199. Binary Tree Right
2019-07-06 本文已影响0人
PJCK
Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
Example:
Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:
1 <---
/ \
2 3 <---
\ \
5 4 <---
思路:
这个题可以用BFS,只要把BFS的队列中添加左子树和右子树中,先加右子树,而且可以设置一个变量,用于统计添加次数,保证每行能够加到最右边的结点的值。
python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 rightSideView(self, root: TreeNode) -> List[int]:
nums = []
Q = []
if not root:
return []
Q.append(root)
while len(Q):
length = len(Q)
i = 0
for i in range(length):
T = Q[0]
Q.pop(0)
i += 1
if i == 1:
nums.append(T.val)
if T.right:
Q.append(T.right)
if T.left:
Q.append(T.left)
return nums
对了 ,如果对于写C++代码是很熟悉的话,可能会不经意的写i++,但是,这个在python上是错误的,应该用i+=1。