删除二叉查找树的节点

给定一棵具有不同节点值的二叉查找树，删除树中与给定值相同的节点。如果树中没有相同值的节点，就不做任何处理。你应该保证处理之后的树仍是二叉查找树。

Steps:

1. Find the node

2. Find the maximum node in the left subtree

3. Replace the node with the maximum node in the left subtree.

Special Cases:

1. The node doest have a left child.

2. The maximum node in the left subtree has a left child.

3. The node is the root of the tree.

public TreeNode removeNode(TreeNode root, int value) {
        TreeNode dummy = new TreeNode(0);
        dummy.left = root;
        
        TreeNode parent = findNode(dummy, root, value);
        if (parent.left != null && parent.left.val == value){
            deleteNode(parent, parent.left);
        }
        if (parent.right != null && parent.right.val == value){
            deleteNode(parent, parent.right);
        }else{
            return dummy.left;
        }
        return dummy.left;
    }
    
    private TreeNode findNode(TreeNode parent, TreeNode node, int value) {
        if (node == null) {
            return parent;
        }
        
        if (node.val == value) {
            return parent;
        }
        if (value < node.val) {
            return findNode(node, node.left, value);
        } else {
            return findNode(node, node.right, value);
        }
    }
    
    private void deleteNode(TreeNode parent, TreeNode node) {
        if (node.left == null){
            if (node == parent.left){
                parent.left = node.right;
            }else {
                parent.right = node.right;
            }
            
        }else if (node.right == null){
            if (node == parent.right){
                parent.right = node.left;
            }else {
                parent.left = node.left;
            }
        }else {
            TreeNode temp = node.right;
            TreeNode father = node;
            while (temp.left != null){
                father = temp;
                temp = temp.left;
            }
            if (father.left == temp){
                father.left =temp.right;
            }else {
                father.right = temp.right;
            }
            node.val = temp.val;
            /*if (parent.left == node) {
                parent.left = temp;
            } else {
                parent.right = temp;
            }
            
            temp.left = node.left;
            temp.right = node.right;*/
        }
    }