From afbd3f7088f587462a2c1c9a27ee65c336ced1aa Mon Sep 17 00:00:00 2001
From: huangbotao <36856212+huangbotao@users.noreply.github.com>
Date: Mon, 16 May 2022 10:53:26 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96=E5=BF=AB=E6=8E=92=E4=BB=A3?=
 =?UTF-8?q?=E7=A0=81?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

1. 重复代码抽取为 swap 方法
2. 添加 随机获取 pivot 的机制
---
 java/12_sorts/QuickSort.java | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/java/12_sorts/QuickSort.java b/java/12_sorts/QuickSort.java
index 08136570..25365d87 100644
--- a/java/12_sorts/QuickSort.java
+++ b/java/12_sorts/QuickSort.java
@@ -1,5 +1,7 @@
 package sorts;
 
+import java.util.concurrent.ThreadLocalRandom;
+
 /**
  * Created by wangzheng on 2018/10/16.
  */
@@ -20,25 +22,27 @@ private static void quickSortInternally(int[] a, int p, int r) {
   }
 
   private static int partition(int[] a, int p, int r) {
+    int pos = ThreadLocalRandom.current().nextInt(l, r + 1);
+    swap(a, pos, r);
     int pivot = a[r];
     int i = p;
     for(int j = p; j < r; ++j) {
       if (a[j] < pivot) {
-        if (i == j) {
-          ++i;
-        } else {
-          int tmp = a[i];
-          a[i++] = a[j];
-          a[j] = tmp;
+        if (i != j) {
+          swap(a,i,j);
         }
+        ++i;
       }
     }
 
-    int tmp = a[i];
-    a[i] = a[r];
-    a[r] = tmp;
+    swap(a,i,r);
 
     System.out.println("i=" + i);
     return i;
   }
+  private static void swap(int[] a, int i, int j) {
+    int temp = a[i];
+    a[i] = a[j];
+    a[j] = temp;
+  }
 }