动态数据流查中位数

Author: huangkui

php/10_heap/findmiddle.php

@@ -0,0 +1,56 @@
+<?php
+namespace Algo_10;
+
+require_once '../vendor/autoload.php';
+
+$arr = [9, 8, 11, 4, 2, 6, 5, 1, -1, 3, 20, 10];
+//$arr=[9,8,11,4,2,6,5,100];
+
+findMiddle($arr);
+
+//动态数据实时获取中位数
+function findMiddle($arr)
+{
+ //大顶堆
+ $bigHeap = new Heap(0, 1);
+ //小顶堆
+ $smallHeap = new Heap(0, 0);
+
+ foreach ($arr as $k => $v) {
+ if ($bigHeap->isEmpty()) {
+ $bigHeap->insert($v);
+ } else {
+ $bigPeak = $bigHeap->peak();
+ if ($v < $bigPeak) {
+ $bigHeap->insert($v);
+ } else {
+ $smallHeap->insert($v);
+ }
+
+ if ($bigHeap->count - $smallHeap->count > 1) {
+ $bigPeak = $bigHeap->deleteFirst();
+ $smallHeap->insert($bigPeak);
+ } elseif ($smallHeap->count - $bigHeap->count > 1) {
+ $smallPeak = $smallHeap->deleteFirst();
+ $bigHeap->insert($smallPeak);
+ }
+
+ }
+ //实时获取中位数
+ echo "现在的中位数为:".implode(',', midPeak($bigHeap, $smallHeap)) . PHP_EOL;
+ }
+
+
+}
+
+function midPeak($heap1, $heap2)
+{
+ if ($heap1->count == $heap2->count) {
+ $midArr = [$heap1->peak(), $heap2->peak()];
+ } elseif ($heap2->count > $heap1->count) {
+ $midArr = [$heap2->peak()];
+ } else {
+ $midArr = [$heap1->peak()];
+ }
+ return $midArr;
+}