#289 Find Median from Data Stream

Author: forest000014

find-median-from-data-stream/forest000014.java

@@ -0,0 +1,49 @@
+/*
+# Time Complexity: O(nlogn)
+# Space Complexity: O(nlogn)
+
+*/
+class MedianFinder {
+
+    private PriorityQueue<Integer> pq1; // 1번째 ~ 가운데 원소 (max heap)
+    private PriorityQueue<Integer> pq2; // 가운데+1번째 ~ 마지막 원소 (min heap)
+
+    public MedianFinder() {
+        pq1 = new PriorityQueue<>(Collections.reverseOrder());
+        pq2 = new PriorityQueue<>();
+    }
+
+    public void addNum(int num) {
+
+        if (pq1.size() == pq2.size()) {
+            if (pq1.peek() == null || pq1.peek() >= num) {
+                pq1.add(num);
+            } else {
+                pq2.add(num);
+                pq1.add(pq2.poll());
+            }
+        } else {
+            if (pq1.peek() == null || pq1.peek() >= num) {
+                pq1.add(num);
+                pq2.add(pq1.poll());
+            } else {
+                pq2.add(num);
+            }
+        }
+    }
+
+    public double findMedian() {
+        if (pq1.size() == pq2.size()) {
+            return (pq1.peek() + pq2.peek()) / 2.0;
+        } else {
+            return pq1.peek();
+        }
+    }
+}
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * MedianFinder obj = new MedianFinder();
+ * obj.addNum(num);
+ * double param_2 = obj.findMedian();
+ */