/**

* 814. Binary Tree Pruning

* https://leetcode.com/problems/binary-tree-pruning/

* Difficulty: Medium

*

* 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.

*/

/**

* 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 null;

root.left = pruneTree(root.left);

root.right = pruneTree(root.right);

if (!root.left && !root.right && root.val === 0) {

return null;

}

return root;

};