增加530二叉搜索树的最小绝对差.md js递归与迭代解法

Author: martisss

problems/0530.二叉搜索树的最小绝对差.md

@@ -265,7 +265,7 @@ func getMinimumDifference(root *TreeNode) int {
 ```
 
 ## JavaScript 
-
+递归 先转换为有序数组
 ```javascript
 /**
  * Definition for a binary tree node.
@@ -297,6 +297,47 @@ var getMinimumDifference = function (root) {
     return diff;
 };
 ```
+递归 在递归的过程中更新最小值
+```js
+var getMinimumDifference = function(root) {
+    let res = Infinity
+    let preNode = null
+    // 中序遍历
+    const inorder = (node) => {
+        if(!node) return
+        inorder(node.left)
+        // 更新res
+        if(preNode) res = Math.min(res, node.val - preNode.val)
+        // 记录前一个节点         
+        preNode = node
+        inorder(node.right)
+    }
+    inorder(root)
+    return res
+}
+```
+
+迭代  中序遍历
+```js
+var getMinimumDifference = function(root) {
+    let stack = []
+    let cur = root
+    let res = Infinity
+    let pre = null
+    while(cur || stack.length) {
+        if(cur) {
+            stack.push(cur)
+            cur = cur.left
+        } else {
+            cur = stack.pop()
+            if(pre) res = Math.min(res, cur.val - pre.val)
+            pre = cur
+            cur = cur.right
+        }
+    }
+    return res
+}
+```
 
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)