BAEL-1773 Find the middle element of a Linked List. (#4350)

* BAEL-1773 - find middle element of linked list * changes from review * changes from review
2018-05-28 21:20:37 +02:00
parent 14a1b90ed9
commit 260e805b69
3 changed files with 195 additions and 0 deletions
@@ -0,0 +1,58 @@
+package com.baeldung.linkedlist;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class MiddleElementLookupUnitTest {
+
+    @Test
+    public void whenFindingMiddle_thenMiddleFound() {
+        String middle = MiddleElementLookup.findMiddleElement(createList(5).head());
+        assertEquals("3", middle);
+
+        middle = MiddleElementLookup.findMiddleElement(createList(4).head());
+        assertEquals("2", middle);
+    }
+
+    @Test
+    public void whenFindingMiddle1PassRecursively_thenMiddleFound() {
+        String middle = MiddleElementLookup.findMiddleElement1PassRecursively(createList(5).head());
+        assertEquals("3", middle);
+
+        middle = MiddleElementLookup.findMiddleElement1PassRecursively(createList(4).head());
+        assertEquals("2", middle);
+    }
+
+    @Test
+    public void whenFindingMiddle1PassIteratively_thenMiddleFound() {
+        String middle = MiddleElementLookup.findMiddleElement1PassIteratively(createList(5).head());
+        assertEquals("3", middle);
+
+        middle = MiddleElementLookup.findMiddleElement1PassIteratively(createList(4).head());
+        assertEquals("2", middle);
+    }
+
+    @Test
+    public void whenListEmptyOrNull_thenMiddleNull() {
+        String middle = MiddleElementLookup.findMiddleElement(null);
+        assertEquals(null, middle);
+
+        middle = MiddleElementLookup.findMiddleElement1PassIteratively(null);
+        assertEquals(null, middle);
+
+        middle = MiddleElementLookup.findMiddleElement1PassRecursively(null);
+        assertEquals(null, middle);
+    }
+
+    private static LinkedList createList(int n) {
+        LinkedList list = new LinkedList();
+
+        for (int i = 1; i <= n; i++) {
+            list.add(String.valueOf(i));
+        }
+
+        return list;
+    }
+
+}