Efficient Median Finder Using Two Heaps in Java

This implementation provides an optimized solution for finding the median of a dynamically updating data stream. It uses two priority queues (heaps) to maintain balance between the lower and upper halves of the dataset. The max heap stores the smaller half of the elements, while the min heap stores the larger half.

Author: Mandru-JashwanthKumar

LeetcodeProblems/295-find-median-from-data-stream.java

@@ -1,23 +1,37 @@
+import java.util.Collections;
+import java.util.PriorityQueue;
+import java.util.Queue;
+
 class MedianFinder {
-  public void addNum(int num) {
-    if (maxHeap.isEmpty() || num <= maxHeap.peek())
-      maxHeap.offer(num);
-    else
-      minHeap.offer(num);
 
-    
-    if (maxHeap.size() < minHeap.size())
-      maxHeap.offer(minHeap.poll());
-    else if (maxHeap.size() - minHeap.size() > 1)
-      minHeap.offer(maxHeap.poll());
-  }
+    private Queue<Integer> maxHeap;
+    private Queue<Integer> minHeap;
+
+    public MedianFinder() {
+        maxHeap = new PriorityQueue<>(Collections.reverseOrder()); 
+        minHeap = new PriorityQueue<>(); 
+    }
+
+    public void addNum(int num) {
+        
+        if (maxHeap.isEmpty() || num <= maxHeap.peek()) {
+            maxHeap.offer(num);
+        } else {
+            minHeap.offer(num);
+        }
 
-  public double findMedian() {
-    if (maxHeap.size() == minHeap.size())
-      return (double) (maxHeap.peek() + minHeap.peek()) / 2.0;
-    return (double) maxHeap.peek();
-  }
+        
+        if (maxHeap.size() < minHeap.size()) {
+            maxHeap.offer(minHeap.poll());
+        } else if (maxHeap.size() - minHeap.size() > 1) {
+            minHeap.offer(maxHeap.poll());
+        }
+    }
 
-  private Queue<Integer> maxHeap = new PriorityQueue<>(Collections.reverseOrder());
-  private Queue<Integer> minHeap = new PriorityQueue<>();
-}
+    public double findMedian() {
+        if (maxHeap.size() == minHeap.size()) {
+            return (maxHeap.peek() + minHeap.peek()) / 2.0;
+        }
+        return maxHeap.peek();
+    }
+}