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Binary Tree Pruning

Problem statement​

Given the root of a binary tree, return the same tree where every subtree (of the given tree) not containing a 1 has been removed.

A subtree of a node node is node plus every node that is a descendant of node.

Example 1:

Input: root = [1,null,0,0,1]Output: [1,null,0,null,1]Explanation: Only the red nodes satisfy the property "every subtree not containing a 1".The diagram on the right represents the answer.

Example 2:

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

Example 3:

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

Constraints:

  • The number of nodes in the tree is in the range [1, 200].
  • Node.val is either 0 or 1.

My solution​

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
var pruneTree = function(root) {
    if (!root) {
        return false;
    }
    if (root.left) {
        root.left = pruneTree(root.left)
    }
    if (root.right) {
        root.right = pruneTree(root.right)
    }
    
    return (root.val || root.left || root.right) ? root : null;
};