week 3 450. Delete Node in a BST

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
   public TreeNode deleteNode(TreeNode root, int key) {
    if(root == null){
        return null;
    }
    if(key < root.val){
        root.left = deleteNode(root.left, key); 
    }else if(key > root.val){
        root.right = deleteNode(root.right, key);
    }else{
        if(root.left == null){
            return root.right; 
        }else if(root.right == null){
            return root.left; 
        }
        
        TreeNode minNode = findMax(root.left);
        root.val = minNode.val;
        root.left = deleteNode(root.left, root.val);
    }
    return root;
}

private TreeNode findMax(TreeNode node){
    while(node.right != null){
        node = node.right;
    }
    return node;
}
       
}