[Leetcode][python] 257: binary tree paths - DFS

• Leetcode 257 Binary tree paths 
• Level: Easy
• Link

Binary Tree Paths - LeetCode

My approach

Classic dfs problem with a tree data structure

1. Check if a root has left or right leaf
2. If either the left or right leaf exists:
   1. perform dfs recursively with the left/right leaf set as the root
3. If none of the left or right leaf exists:
   1. Append the path to the answer array

class Solution:

    def binaryTreePaths(self, root: TreeNode) -> List[str]:
        
        def dfs(node, path):
            path += '->'
            path += str(node.val)

            if not node.left and not node.right:
                return ans.append(path[2:])

            if node.left:
                dfs(node.left, path)

            if node.right:
                dfs(node.right, path)
            
        ans = []
        dfs(root, "")
        return ans