Binary Tree Pruning

Input: root = [1,null,0,0,1]

Output: [1,null,0,null,1]

Only nodes that are part of a subtree containing a 1 are kept. The left child of the 0 node (which was 0) is removed since that subtree contains no 1s.

Input: root = [1,0,1,0,0,0,1]

Output: [1,null,1,null,1]

The entire left subtree of the root (rooted at 0) is removed because it contains no 1s. The left subtree of the right child (also 0) is removed for the same reason.

Input: root = [1,1,0,1,1,0,1,0]

Output: [1,1,0,1,1,null,1]

Most of the tree is preserved since there are 1s throughout. Only the leftmost leaf (0) and one subtree containing only 0s are pruned.

Binary Tree Pruning

Problem

Constraints

Examples