fix: add solution and testcase (#156)

Author: ashmichheda

src/main/java/com/fishercoder/solutions/_1290.java

@@ -13,4 +13,15 @@ public int getDecimalValue(ListNode head) {
             return Integer.parseInt(sb.toString(), 2);
         }
     }
+    public static class Solution2 {
+        public int getDecimalValue(ListNode head) {
+            int sum = 0;
+            while (head != null) {
+                sum *= 2;
+                sum += head.val;
+                head = head.next;
+            }
+            return sum;
+        }
+    }
 }

src/test/java/com/fishercoder/_1290Test.java

@@ -12,17 +12,23 @@
 
 public class _1290Test {
     private static _1290.Solution1 solution1;
+    private static _1290.Solution2 solution2;
     private static ListNode head;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _1290.Solution1();
+        solution2 = new _1290.Solution2();
     }
 
     @Test
     public void test1() {
         head = LinkedListUtils.createSinglyLinkedList(Arrays.asList(1, 0, 1));
         assertEquals(5, solution1.getDecimalValue(head));
     }
-
+    @Test
+    public void test2() {
+        head = ListNode.createSinglyLinkedList(Arrays.asList(1, 1, 1));
+        assertEquals(7, solution2.getDecimalValue(head));
+    }
 }