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LeetCode solutions

1030. Smallest String Starting From Leaf

My accepted Python solution to LeetCode problem 1030, Smallest String Starting From Leaf, running in 7ms.

  • Difficulty: Medium
  • Python
  • Runtime 7ms
  • Memory 18.3MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 7ms, memory 18.3MB, accepted 2026-01-01.

python
class Solution:
    def smallestFromLeaf(self, root: Optional[TreeNode]) -> str:
        self.result = None
        
        def dfs(node, path):
            if not node:
                return
            path = chr(ord('a') + node.val) + path
            if not node.left and not node.right:
                if self.result is None or path < self.result:
                    self.result = path
                return
            dfs(node.left, path)
            dfs(node.right, path)
        
        dfs(root, "")
        return self.result

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