add solution and testcase for 1836 (#159)

ashmichheda · web-flow · commit 7b6184bf98d1 · 2021-08-29T12:10:03.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_1836.java b/src/main/java/com/fishercoder/solutions/_1836.java
@@ -0,0 +1,31 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.ListNode;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class _1836 {
+    public static class Solution1 {
+        public ListNode removeDuplicates(ListNode head) {
+            // write your code here
+            // Maintain a hashtable to checkup for duplicate element in constant time
+            Set<Integer> uniqueNums = new HashSet<>();
+
+            ListNode current = head;
+            ListNode prev = null;
+            while (current != null) {
+                int val = current.val;
+                if (uniqueNums.contains(val)) {
+                    prev.next = current.next;
+                }
+                else {
+                    uniqueNums.add(val);
+                    prev = current;
+                }
+                current = current.next;
+            }
+            return head;
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1836Test.java b/src/test/java/com/fishercoder/_1836Test.java
@@ -0,0 +1,25 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.ListNode;
+import com.fishercoder.solutions._1836;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1836Test {
+    private static _1836.Solution1 solution1;
+    private static ListNode head;
+    private static ListNode result;
+    @BeforeClass
+    public static void setup() { solution1 = new _1836.Solution1(); }
+
+    @Test
+    public void test1() {
+        head = ListNode.createSinglyLinkedList(Arrays.asList(1, 2, 1, 3, 3, 5, 6, 3));
+        result = solution1.removeDuplicates(head);
+        assertEquals(result, ListNode.createSinglyLinkedList(Arrays.asList(1, 2, 3, 5, 6)));
+    }
+}
