题目：

题解：

class Solution {public TreeNode deleteNode(TreeNode root, int key) {TreeNode cur = root, curParent = null;while (cur != null && cur.val != key) {curParent = cur;if (cur.val > key) {cur = cur.left;} else {cur = cur.right;}}if (cur == null) {return root;}if (cur.left == null && cur.right == null) {cur = null;} else if (cur.right == null) {cur = cur.left;} else if (cur.left == null) {cur = cur.right;} else {TreeNode successor = cur.right, successorParent = cur;while (successor.left != null) {successorParent = successor;successor = successor.left;}if (successorParent.val == cur.val) {successorParent.right = successor.right;} else {successorParent.left = successor.right;}successor.right = cur.right;successor.left = cur.left;cur = successor;}if (curParent == null) {return cur;} else {if (curParent.left != null && curParent.left.val == key) {curParent.left = cur;} else {curParent.right = cur;}return root;}}
}