二叉树part08

235. 二叉搜索树的最近公共祖先

前序，利用二叉搜索的特性

/*** Definition for a binary tree node.* function TreeNode(val) {*     this.val = val;*     this.left = this.right = null;* }*//*** @param {TreeNode} root* @param {TreeNode} p* @param {TreeNode} q* @return {TreeNode}*/
var lowestCommonAncestor = function(root, p, q) {if(!root) return null;//如果等于p或q就返回if(root === p || root === q) return root;if((p.val < root.val && q.val > root.val) || (p.val > root.val && q.val < root.val)) return root;if(p.val > root.val && q.val > root.val){return lowestCommonAncestor(root.right, p, q);}else if(p.val < root.val && q.val < root.val){return lowestCommonAncestor(root.left, p, q)}
};

701. 二叉搜索树中的插入操作

/*** Definition for a binary tree node.* function TreeNode(val, left, right) {*     this.val = (val===undefined ? 0 : val)*     this.left = (left===undefined ? null : left)*     this.right = (right===undefined ? null : right)* }*/
/*** @param {TreeNode} root* @param {number} val* @return {TreeNode}*/
var insertIntoBST = function(root, val) {if(!root){//找到插入点let node = new TreeNode(val);return node;}if(root.val > val){root.left = insertIntoBST(root.left, val);}else if(root.val < val){root.right = insertIntoBST(root.right, val);}return root;
};

450. 删除二叉搜索树中的节点

/*** Definition for a binary tree node.* function TreeNode(val, left, right) {*     this.val = (val===undefined ? 0 : val)*     this.left = (left===undefined ? null : left)*     this.right = (right===undefined ? null : right)* }*/
/*** @param {TreeNode} root* @param {number} key* @return {TreeNode}*///回溯
var deleteNode = function(root, key) {//如果删除节点5//有三种情况//1.两个孩子都有 :让较小的孩子成为较大的孩子的孩子//假设right孩子大//操作root.left.right = root.right//只有一个孩子,让孩子替代自己 };function deleteNode(node, key){if(!node) return null;deleteNode()}