MedianFinder2

Author: masx200

find-median-from-data-stream/MedianFinder.ts

@@ -0,0 +1,34 @@
+import { Heap } from "../deps.ts";
+
+export default class MedianFinder {
+    #min: Heap<number>;
+    #max: Heap<number>;
+    constructor() {
+        this.#min = new Heap((a, b) => a - b);
+        this.#max = new Heap((a, b) => b - a);
+    }
+    addNum(num: number) {
+        const max = this.#max,
+            min = this.#min;
+        const m = max.size(),
+            n = min.size();
+        if (m == n) {
+            // 两个堆数目相等:m=n
+            min.insert(num);
+            max.insert(min.pop());
+        } else {
+            // 两个堆数目不相等:m=n+1
+            max.insert(num);
+            min.insert(max.pop());
+        }
+    }
+    findMedian() {
+        const max = this.#max,
+            min = this.#min;
+        if (max.size() === min.size()) {
+            return (max.top() + min.top()) / 2;
+        } else {
+            return max.top();
+        }
+    }
+}

find-median-from-data-stream/test.ts

@@ -1,8 +1,18 @@
 import { assertEquals } from "../deps.ts";
-import MedianFinder from "./index.ts";
+import MedianFinder1 from "./index.ts";
+import MedianFinder2 from "./MedianFinder.ts";
 
-Deno.test("find-median-from-data-stream", () => {
-    const medianFinder = new MedianFinder();
+Deno.test("find-median-from-data-stream-1", () => {
+    const medianFinder = new MedianFinder1();
+
+    medianFinder.addNum(1);
+    medianFinder.addNum(2);
+    assertEquals(medianFinder.findMedian(), 1.5);
+    medianFinder.addNum(3);
+    assertEquals(medianFinder.findMedian(), 2);
+});
+Deno.test("find-median-from-data-stream-2", () => {
+    const medianFinder = new MedianFinder2();
 
     medianFinder.addNum(1);
     medianFinder.addNum(2);