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1157. Insufficient Nodes in Root to Leaf Paths

My accepted Python solution to LeetCode problem 1157, Insufficient Nodes in Root to Leaf Paths, running in 8ms.

  • Difficulty: Medium
  • Python
  • Runtime 8ms
  • Memory 18.6MB

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 8ms, memory 18.6MB, accepted 2026-01-02.

python
# 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 sufficientSubset(self, root: Optional[TreeNode], limit: int) -> Optional[TreeNode]:
        def dfs(node, current_sum):
            if not node:
                return None
            
            current_sum += node.val
            
            # If it's a leaf node
            if not node.left and not node.right:
                # Return None if the path sum is less than limit
                if current_sum < limit:
                    return None
                return node
            
            # Recursively process children
            node.left = dfs(node.left, current_sum)
            node.right = dfs(node.right, current_sum)
            
            # If both children are removed, remove this node too
            if not node.left and not node.right:
                return None
            
            return node
        
        return dfs(root, 0)

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