199. Binary Tree Right Side View

https://leetcode.com/problems/binary-tree-right-side-view/

Python

• 102. Level Order的變形

class Solution:
    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        return self._travel(root, 0, [])

    def _travel(self, node, level, result):
        if not node:
            return result

        if len(result) < level+1:
            result.append(None)

        result[level] = node.val

        self._travel(node.left, level+1, result)
        self._travel(node.right, level+1, result)

        return result