Update 295-find-median-from-data-stream.js

Author: everthis

295-find-median-from-data-stream.js

@@ -38,3 +38,107 @@ MedianFinder.prototype.findMedian = function() {
  * obj.addNum(num)
  * var param_2 = obj.findMedian()
  */
+
+// another
+
+/**
+ * initialize your data structure here.
+ */
+const MedianFinder = function() {
+  this.minPQ = new PriorityQueue()
+  this.maxPQ = new PriorityQueue((a, b) => a < b)
+};
+
+/** 
+ * @param {number} num
+ * @return {void}
+ */
+MedianFinder.prototype.addNum = function(num) {
+  this.minPQ.push(num)
+  this.maxPQ.push(this.minPQ.pop())
+  if(this.minPQ.size() < this.maxPQ.size()) {
+    this.minPQ.push(this.maxPQ.pop())
+  }
+};
+
+/**
+ * @return {number}
+ */
+MedianFinder.prototype.findMedian = function() {
+  if(this.minPQ.size() > this.maxPQ.size()) return this.minPQ.peek()
+  else return (this.minPQ.peek() + this.maxPQ.peek()) / 2
+};
+
+/** 
+ * Your MedianFinder object will be instantiated and called as such:
+ * var obj = new MedianFinder()
+ * obj.addNum(num)
+ * var param_2 = obj.findMedian()
+ */
+class PriorityQueue {
+  constructor(comparator = (a, b) => a > b) {
+    this.heap = []
+    this.top = 0
+    this.comparator = comparator
+  }
+  size() {
+    return this.heap.length
+  }
+  isEmpty() {
+    return this.size() === 0
+  }
+  peek() {
+    return this.heap[this.top]
+  }
+  push(...values) {
+    values.forEach((value) => {
+      this.heap.push(value)
+      this.siftUp()
+    })
+    return this.size()
+  }
+  pop() {
+    const poppedValue = this.peek()
+    const bottom = this.size() - 1
+    if (bottom > this.top) {
+      this.swap(this.top, bottom)
+    }
+    this.heap.pop()
+    this.siftDown()
+    return poppedValue
+  }
+  replace(value) {
+    const replacedValue = this.peek()
+    this.heap[this.top] = value
+    this.siftDown()
+    return replacedValue
+  }
+
+  parent = (i) => ((i + 1) >>> 1) - 1
+  left = (i) => (i << 1) + 1
+  right = (i) => (i + 1) << 1
+  greater = (i, j) => this.comparator(this.heap[i], this.heap[j])
+  swap = (i, j) => ([this.heap[i], this.heap[j]] = [this.heap[j], this.heap[i]])
+  siftUp = () => {
+    let node = this.size() - 1
+    while (node > this.top && this.greater(node, this.parent(node))) {
+      this.swap(node, this.parent(node))
+      node = this.parent(node)
+    }
+  }
+  siftDown = () => {
+    let node = this.top
+    while (
+      (this.left(node) < this.size() && this.greater(this.left(node), node)) ||
+      (this.right(node) < this.size() && this.greater(this.right(node), node))
+    ) {
+      let maxChild =
+        this.right(node) < this.size() &&
+        this.greater(this.right(node), this.left(node))
+          ? this.right(node)
+          : this.left(node)
+      this.swap(node, maxChild)
+      node = maxChild
+    }
+  }
+}