Binary tree paths

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def binaryTreePaths(self, root: Optional[TreeNode]) -> List[str]:
        res = []
        path = []
        def backtrack(node):
            path.append(node.val)
            if not node.left and not node.right:
                res.append("->".join(map(str, path)))
                return
            if node.left:
                backtrack(node.left)
                path.pop()
            if node.right:
                backtrack(node.right)
                path.pop()

        backtrack(root)

        return res

Binary Tree Paths

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Given the root of a binary tree, return all root-to-leaf paths in any order.

A leaf is a node with no children.

 

Example 1:

Input: root = [1,2,3,null,5]
Output: ["1->2->5","1->3"]

Example 2:

Input: root = [1]
Output: ["1"]

 

Constraints:

• The number of nodes in the tree is in the range [1, 100].
• -100 <= Node.val <= 100