Middle of the linked list (examplehub#89)

realDuYuanChao · github-actions · web-flow · commit 7018c36b6a6c · 2021-03-28T12:29:24.000+08:00
* middle-of-the-linked-list

* Formatted with Google Java Formatter

Co-authored-by: github-actions &lt;${GITHUB_ACTOR}@users.noreply.github.com&gt;
diff --git a/src/main/java/com/examplehub/leetcode/easy/MiddleOfTheLinkedList.java b/src/main/java/com/examplehub/leetcode/easy/MiddleOfTheLinkedList.java
@@ -0,0 +1,31 @@
+package com.examplehub.leetcode.easy;
+
+import com.examplehub.leetcode.ListNode;
+
+/** https://leetcode.com/problems/middle-of-the-linked-list/ */
+public class MiddleOfTheLinkedList {
+
+  public static ListNode solution1(ListNode head) {
+    int len = 0;
+    ListNode p = head;
+    while (p != null) {
+      len++;
+      p = p.next;
+    }
+    p = head;
+    for (int i = 1; i <= len / 2; i++) {
+      p = p.next;
+    }
+    return p;
+  }
+
+  public static ListNode solution2(ListNode head) {
+    ListNode p1 = head;
+    ListNode p2 = head;
+    while (p1 != null && p1.next != null) {
+      p1 = p1.next.next;
+      p2 = p2.next;
+    }
+    return p2;
+  }
+}
diff --git a/src/test/java/com/examplehub/leetcode/easy/MiddleOfTheLinkedListTest.java b/src/test/java/com/examplehub/leetcode/easy/MiddleOfTheLinkedListTest.java
@@ -0,0 +1,70 @@
+package com.examplehub.leetcode.easy;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.examplehub.leetcode.ListNode;
+import org.junit.jupiter.api.Test;
+
+class MiddleOfTheLinkedListTest {
+  @Test
+  void testSolution1() {
+    ListNode head = new ListNode(1);
+    ListNode node2 = new ListNode(2);
+    ListNode node3 = new ListNode(3);
+    ListNode node4 = new ListNode(4);
+    ListNode node5 = new ListNode(5);
+
+    head.next = node2;
+    node2.next = node3;
+    node3.next = node4;
+    node4.next = node5;
+
+    assertSame(node3, MiddleOfTheLinkedList.solution1(head));
+
+    head = new ListNode(1);
+    node2 = new ListNode(2);
+    node3 = new ListNode(3);
+    node4 = new ListNode(4);
+    node5 = new ListNode(5);
+    ListNode node6 = new ListNode(6);
+
+    head.next = node2;
+    node2.next = node3;
+    node3.next = node4;
+    node4.next = node5;
+    node5.next = node6;
+
+    assertSame(node4, MiddleOfTheLinkedList.solution1(head));
+  }
+
+  @Test
+  void testSolution2() {
+    ListNode head = new ListNode(1);
+    ListNode node2 = new ListNode(2);
+    ListNode node3 = new ListNode(3);
+    ListNode node4 = new ListNode(4);
+    ListNode node5 = new ListNode(5);
+
+    head.next = node2;
+    node2.next = node3;
+    node3.next = node4;
+    node4.next = node5;
+
+    assertSame(node3, MiddleOfTheLinkedList.solution2(head));
+
+    head = new ListNode(1);
+    node2 = new ListNode(2);
+    node3 = new ListNode(3);
+    node4 = new ListNode(4);
+    node5 = new ListNode(5);
+    ListNode node6 = new ListNode(6);
+
+    head.next = node2;
+    node2.next = node3;
+    node3.next = node4;
+    node4.next = node5;
+    node5.next = node6;
+
+    assertSame(node4, MiddleOfTheLinkedList.solution2(head));
+  }
+}
