814. Binary Tree Pruning

// 814. Binary Tree Pruning
// Runtime: 0 ms, faster than 100.00% of Java online submissions for Binary Tree Pruning.
// Memory Usage: 36.1 MB, less than 97.31% of Java online submissions for Binary Tree Pruning.






/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode pruneTree(TreeNode root) {
            
        helperFunction(root);
        
        if(root.val==0 && root.left==null && root.right==null)
            return null;
        
        return root;
    }
    
    public void helperFunction(TreeNode root){
        
         if(root.left!=null)
        helperFunction(root.left);
        
        if(root.right!=null)
        helperFunction(root.right);
        
        
        if(root.left!=null && root.left.val==0){
            if(root.left.left==null && root.left.right==null){
                root.left=null;
            }
        }
        if(root.right!=null && root.right.val==0){
            if(root.right.left==null && root.right.right==null){
                root.right=null;
            }
        }
        
        
       
    }
    
}