https://leetcode.com/problems/delete-node-in-a-bst/
删除BST中的指定节点
如果当前节点为要删除的，可以把左子节点或者右子节点移动上来，模块化即可
public class Solution { public TreeNode deleteNode(TreeNode root, int key) { // 有可能要删除的点不存在 if (root == null) { return null; } if (root.val == key) { return adjust(root); } else if (root.val > key) { root.left = deleteNode(root.left, key); } else { root.right = deleteNode(root.right, key); } return root; } private TreeNode adjust(TreeNode root) { TreeNode ret = null; if (root.left != null) { ret = root.left; TreeNode rightest = getRight(root.left); rightest.right = root.right; } else if (root.right != null) { ret = root.right; TreeNode leftest = getLeft(root.right); leftest.left = root.left; } return ret; } private TreeNode getRight(TreeNode root) { while (root.right != null) { root = root.right; } return root; } private TreeNode getLeft(TreeNode root) { while (root.left != null) { root = root.left; } return root; } }