From d30a8c82da5e30f0f25296f7f5936a5b2cda8ee3 Mon Sep 17 00:00:00 2001
From: Wouter Groeneveld <wouter.groeneveld@gmail.com>
Date: Mon, 9 Apr 2018 15:49:34 +0200
Subject: [PATCH] http://www.brainbaking.com/post/pseudocode/

---
 .../java/src/be/brainbaking/lists/Lists.java  |  4 ++++
 .../be/brainbaking/lists/ListsWrapper.java    | 22 +++++++++++++++++++
 .../src/be/brainbaking/sorting/QuickSort.java |  5 +++--
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 sorting/java/src/be/brainbaking/lists/ListsWrapper.java

diff --git a/sorting/java/src/be/brainbaking/lists/Lists.java b/sorting/java/src/be/brainbaking/lists/Lists.java
index 4ec0c96..4f30384 100644
--- a/sorting/java/src/be/brainbaking/lists/Lists.java
+++ b/sorting/java/src/be/brainbaking/lists/Lists.java
@@ -5,6 +5,10 @@ import java.util.stream.Collectors;
 
 public class Lists {
 
+    public static ListsWrapper exchange(int oneBasedA) {
+        return new ListsWrapper(oneBasedA);
+    }
+
     public static void swap(List<Integer> list, int oneBasedA, int oneBasedB) {
         int temp = list.get(oneBasedA - 1);
         list.set(oneBasedA - 1, list.get(oneBasedB - 1));
diff --git a/sorting/java/src/be/brainbaking/lists/ListsWrapper.java b/sorting/java/src/be/brainbaking/lists/ListsWrapper.java
new file mode 100644
index 0000000..1f75b57
--- /dev/null
+++ b/sorting/java/src/be/brainbaking/lists/ListsWrapper.java
@@ -0,0 +1,22 @@
+package be.brainbaking.lists;
+
+import java.util.List;
+
+public class ListsWrapper {
+
+    private final int oneBasedA;
+    private int oneBasedB;
+
+    public ListsWrapper with(int oneBasedB) {
+        this.oneBasedB = oneBasedB;
+        return this;
+    }
+
+    public void in(List<Integer> list) {
+        Lists.swap(list, oneBasedA, oneBasedB);
+    }
+
+    public ListsWrapper(int oneBasedA) {
+        this.oneBasedA = oneBasedA;
+    }
+}
diff --git a/sorting/java/src/be/brainbaking/sorting/QuickSort.java b/sorting/java/src/be/brainbaking/sorting/QuickSort.java
index 9a81d1a..2870ad4 100644
--- a/sorting/java/src/be/brainbaking/sorting/QuickSort.java
+++ b/sorting/java/src/be/brainbaking/sorting/QuickSort.java
@@ -6,6 +6,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import static be.brainbaking.lists.Lists.asString;
+import static be.brainbaking.lists.Lists.exchange;
 
 public class QuickSort implements Sortable {
 
@@ -68,11 +69,11 @@ public class QuickSort implements Sortable {
         for(int j = oneBasedStartIndex; j <= oneBasedEndIndex - 1; j++) {
             if(list.get(j - 1) <= x) {
                 i++;
-                Lists.swap(list, i, j);
+                exchange(i).with(j).in(list);
             }
         }
 
-        Lists.swap(list, i + 1, oneBasedEndIndex);
+        exchange(i + 1).with(oneBasedEndIndex).in(list);
         System.out.println("partitioned: " + asString(list));
         return i + 1;
     }