feat: adds amiyah jones' lesson12 & stack java files

lesson_12/structs_java/structs_app/src/main/java/com/codedifferently/lesson12/Lesson12.java

@@ -2,11 +2,28 @@
 
 public class Lesson12 {
 
-  /**
-   * Provide the solution to LeetCode 3062 here:
-   * https://github.com/yang-su2000/Leetcode-algorithm-practice/tree/master/3062-winner-of-the-linked-list-game
-   */
   public String gameResult(ListNode head) {
-    return null;
+
+    int oddPoints = 0;
+    int evenPoints = 0;
+
+    ListNode current = head;
+
+    while (current != null && current.next != null) {
+      if (current.val > current.next.val) {
+        evenPoints++;
+      } else if (current.val < current.next.val) {
+        oddPoints++;
+      }
+      current = current.next.next;
+    }
+
+    if (oddPoints > evenPoints) {
+      return "Odd";
+    } else if (evenPoints > oddPoints) {
+      return "Even";
+    } else {
+      return "Tie";
+    }
   }
 }

lesson_12/structs_java/structs_app/src/main/java/com/codedifferently/lesson12/Stack.java

@@ -1,5 +1,7 @@
 package com.codedifferently.lesson12;
 
+import java.util.EmptyStackException;
+
 /** Implement the below Stack by providing code for the class methods. */
 public class Stack {
   private ListNode top;
@@ -9,18 +11,29 @@ public Stack() {
   }
 
   public void push(int value) {
-    // Your code here
+    ListNode newNode = new ListNode(value);
+    newNode.next = top;
+    top = newNode;
   }
 
   public int pop() {
-    return 0;
+    if (isEmpty()) {
+      throw new EmptyStackException();
+    } else {
+      int value = top.val;
+      top = top.next;
+      return value;
+    }
   }
 
   public int peek() {
-    return 0;
+    if (isEmpty()) {
+      throw new EmptyStackException();
+    }
+    return top.val;
   }
 
   public boolean isEmpty() {
-    return true;
+    return top == null;
   }
 }