450. Delete Node in a BST

Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.

Basically, the deletion can be divided into two stages:

1. Search for a node to remove.
2. If the node is found, delete the node.

Note: Time complexity should be O(height of tree).

Example:

root = [5,3,6,2,4,null,7]key = 3    5   / \  3   6 / \   \2   4   7Given key to delete is 3. So we find the node with value 3 and delete it.One valid answer is [5,4,6,2,null,null,7], shown in the following BST.    5   / \  4   6 /     \2       7Another valid answer is [5,2,6,null,4,null,7].    5   / \  2   6   \   \    4   7

思路：递归找到要删除的节点root，然后在右子树root.right中找一个最小的node（也可以在左子树找最大的）minNode，然后把root.left放到minNode.left

package l450;public class Solution {    public TreeNode deleteNode(TreeNode root, int key) {        if(root == null)return root;                if(root.val < key) root.right = deleteNode(root.right, key);        else if(root.val > key)root.left = deleteNode(root.left, key);        else {        if(root.left == null)return root.right;        if(root.right == null)return root.left;                // find right smallest        TreeNode rigthSmallest = root.right;        while(rigthSmallest.left != null)rigthSmallest = rigthSmallest.left;                // change structure of tree        rigthSmallest.left = root.left;        return root.right;        }                return root;    }}