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1080. Insufficient Nodes in Root to Leaf Paths

MediumTree Preparing judge… LeetCode

Given the root of a binary tree and an integer limit, delete all insufficient nodes in the tree simultaneously, and return the root of the resulting binary tree.

A node is insufficient if every root to leaf path intersecting this node has a sum strictly less than limit.

A leaf is a node with no children.

 

Example 1:

Input: root = [1,2,3,4,-99,-99,7,8,9,-99,-99,12,13,-99,14], limit = 1
Output: [1,2,3,4,null,null,7,8,9,null,14]

Example 2:

Input: root = [5,4,8,11,null,17,4,7,1,null,null,5,3], limit = 22
Output: [5,4,8,11,null,17,4,7,null,null,null,5]

Example 3:

Input: root = [1,2,-3,-5,null,4,null], limit = -1
Output: [1,null,-3,4]

 

Constraints:

  • The number of nodes in the tree is in the range [1, 5000].
  • -105 <= Node.val <= 105
  • -109 <= limit <= 109
TreeDepth-First SearchBinary Tree

Hints

Hint 1
Consider a DFS traversal of the tree. You can keep track of the current path sum from root to this node, and you can also use DFS to return the maximum value of any path from this node to the leaf. This will tell you if this node is insufficient.