LeetCode-199 二叉树的右视图

Table of Contents

LeetCode-199 二叉树的右视图 #

Solution 1 #

层序遍历 (BFS).

代码如下:

class Solution:
    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        if root is None:
            return []
        p1 = [root]
        ans = []
        while p1:
            p2 = []
            ans.append(p1[-1].val)
            for node in p1:
                if node.left:
                    p2.append(node.left)
                if node.right:
                    p2.append(node.right)
            p1 = p2.copy()
        return ans

Solution 2 #

递归, 用深度决定是否更新到答案中.

代码如下:

class Solution:
    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        ans = []

        def f(root: Optional[TreeNode], d) -> None:
            if root is None:
                return
            if d > len(ans):
                ans.append(root.val)
            f(root.right, d + 1)
            f(root.left, d + 1)
            return 0

        f(root, 1)
        return ans