Improved task 155.

Author: javadev

src.save/main/java/g0101_0200/s0155_min_stack/MinStack.java

@@ -5,6 +5,20 @@
 // #2022_06_25_Time_3_ms_(100.00%)_Space_44.3_MB_(85.39%)
 
 public class MinStack {
+    private static class Node {
+        int min;
+        int data;
+        Node nextNode;
+        Node previousNode;
+
+        public Node(int min, int data, Node previousNode, Node nextNode) {
+            this.min = min;
+            this.data = data;
+            this.previousNode = previousNode;
+            this.nextNode = nextNode;
+        }
+    }
+
     private Node currentNode;
 
     // initialize your data structure here.