Update 栈相关.md

blogs/Algorithm/剑指 Offer/栈相关.md

@@ -33,3 +33,48 @@ class CQueue {
 }
 ```
 
+#### [30. 包含min函数的栈](https://leetcode-cn.com/problems/bao-han-minhan-shu-de-zhan-lcof/)
+
+```java
+class MinStack {
+
+    private Node head;
+
+    public MinStack() {
+    }
+
+    public void push(int x) {
+        if (head == null) {
+            head = new Node(x, x, null);
+        } else {
+            Node next = head;
+            head = new Node(x, Math.min(x, next.min), next);
+        }
+    }
+
+    public void pop() {
+        head = head.next;
+    }
+
+    public int top() {
+        return head.val;
+    }
+
+    public int min() {
+        return head.min;
+    }
+
+    class Node {
+        public int val;
+        public int min;
+        public Node next;
+
+        public Node(int val, int min, Node next) {
+            this.val = val;
+            this.min = min;
+            this.next = next;
+        }
+    }
+}
+```
+