Update 二叉树相关.md

blogs/Algorithm/剑指 Offer/二叉树相关.md

@@ -484,3 +484,29 @@ class Solution {
 }
 ```
 
+#### [33. 二叉搜索树的后序遍历序列](https://leetcode-cn.com/problems/er-cha-sou-suo-shu-de-hou-xu-bian-li-xu-lie-lcof/)
+
+```java
+class Solution {
+
+    public boolean verifyPostorder(int[] postorder) {
+        return helper(postorder, 0, postorder.length - 1);
+    }
+
+    private boolean helper(int[] order, int i, int j) {
+        if (i >= j) {
+            return true;
+        }
+        int p = i;
+        while (order[p] < order[j]) {
+            p++;
+        }
+        int m = p;
+        while (order[p] > order[j]) {
+            p++;
+        }
+        return p == j && helper(order, i, m - 1) && helper(order, m, j - 1);
+    }
+}
+```
+