feat: created Stack class and Game Result logic for Lesson 12

Author: marleomac3

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

@@ -1,12 +1,44 @@
 package com.codedifferently.lesson12;
 
 public class Lesson12 {
+  // node1 node2 node3 node4 null
 
   /**
    * 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;
+    // These vars keep track of the point for the even and odd indicies.
+    int oddPoints = 0;
+    int evenPoints = 0;
+
+    /*
+     * This var will be redeclared throughout the loop and be used
+     * to point to the node pairs.
+     */
+    ListNode curr = head;
+
+    /**
+     * This loop will do two comparisons. The 1st comparison is to determine which index has a
+     * greater value. The 2nd comparison checks which index team is more points
+     */
+    while (curr != null) {
+      if (curr.val > curr.next.val) {
+        evenPoints++;
+      } else if (curr.val < curr.next.val) {
+        oddPoints++;
+      }
+
+      // "curr.next.next" allows for the loop to skip over an index
+      curr = curr.next.next;
+    }
+
+    if (oddPoints > evenPoints) {
+      return "Odd";
+    } else if (oddPoints < evenPoints) {
+      return "Even";
+    } else {
+      return "Tie";
+    }
   }
 }

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

@@ -10,17 +10,25 @@ public Stack() {
 
   public void push(int value) {
     // Your code here
+    ListNode newTop = new ListNode(value);
+    if (top == null) {
+      top = newTop;
+    } else {
+      newTop.next = top;
+    }
   }
 
   public int pop() {
-    return 0;
+    int oldTopVal = top.val;
+    top = top.next;
+    return oldTopVal;
   }
 
   public int peek() {
-    return 0;
+    return top.val;
   }
 
   public boolean isEmpty() {
-    return true;
+    return top == null;
   }
 }