feat: Add KthElementFinder new algorithm with Junit tests

Author: Hardvan

src/main/java/com/thealgorithms/datastructures/heaps/KthElementFinder.java

@@ -0,0 +1,27 @@
+package com.thealgorithms.datastructures.heaps;
+
+import java.util.PriorityQueue;
+
+public class KthElementFinder {
+    public static int findKthLargest(int[] nums, int k) {
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>(k);
+        for (int num : nums) {
+            minHeap.offer(num);
+            if (minHeap.size() > k) {
+                minHeap.poll();
+            }
+        }
+        return minHeap.peek();
+    }
+
+    public static int findKthSmallest(int[] nums, int k) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>((a, b) -> b - a);
+        for (int num : nums) {
+            maxHeap.offer(num);
+            if (maxHeap.size() > k) {
+                maxHeap.poll();
+            }
+        }
+        return maxHeap.peek();
+    }
+}

src/test/java/com/thealgorithms/datastructures/heaps/KthElementFinderTest.java

@@ -0,0 +1,19 @@
+package com.thealgorithms.datastructures.heaps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class KthElementFinderTest {
+    @Test
+    public void testFindKthLargest() {
+        int[] nums = {3, 2, 1, 5, 6, 4};
+        assertEquals(5, KthElementFinder.findKthLargest(nums, 2));
+    }
+
+    @Test
+    public void testFindKthSmallest() {
+        int[] nums = {7, 10, 4, 3, 20, 15};
+        assertEquals(7, KthElementFinder.findKthSmallest(nums, 3));
+    }
+}