LeetCode 1080: Insufficient Nodes in Root to Leaf Paths Solution

Master LeetCode problem 1080 (Insufficient Nodes in Root to Leaf Paths), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1080. Insufficient Nodes in Root to Leaf Paths

Medium

Tree Depth-First Search Binary Tree

Problem Explanation

Explanation

To solve this problem, we can perform a depth-first search (DFS) traversal of the binary tree. At each node, we recursively check if the current path sum from the root to that node is less than the given limit. If the current node is a leaf node and its value is less than the limit, we can return null indicating that this node should be removed. If the current node is not a leaf node, we recursively process its left and right child nodes. If both children are removed (null), we can remove the current node as well.

Time complexity: O(N) where N is the number of nodes in the binary tree. Space complexity: O(H) where H is the height of the binary tree.

Solution Code

class Solution {
    public TreeNode sufficientSubset(TreeNode root, int limit) {
        return dfs(root, limit, 0);
    }
    
    private TreeNode dfs(TreeNode node, int limit, int sum) {
        if (node == null) return null;
        
        sum += node.val;
        
        if (node.left == null && node.right == null) {
            return sum < limit ? null : node;
        }
        
        node.left = dfs(node.left, limit, sum);
        node.right = dfs(node.right, limit, sum);
        
        if (node.left == null && node.right == null) {
            return null;
        }
        
        return node;
    }
}

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