Feat: adds Lesson12.java && Stack.java for NileJackson

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

@@ -7,6 +7,27 @@ public class Lesson12 {
    * 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[] scores = new int[2];
+
+    while (head.next != null) {
+      // Used ChatGpt to help complete this if statement-starting at the logical & operand
+      if (head.val != head.next.val && head.val % 2 == 0) {
+        if (head.val > head.next.val) {
+          scores[head.val % 2]++;
+          // Gpt help ended at the line above
+        } else {
+          scores[head.next.val % 2]++;
+        }
+      }
+      head = head.next;
+    }
+    if (scores[0] == scores[1]) {
+      return "Tie";
+    } else if (scores[0] > scores[1]) {
+      return "Even";
+    } else {
+      return "Odd";
+    }
   }
 }

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 +11,28 @@ 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();
+    }
+    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;
   }
 }