动态数据流查中位数

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;
+}