diff --git a/src/class05/Code04_DoubleLinkedListQuickSort.java b/src/class05/Code04_DoubleLinkedListQuickSort.java
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+package class05;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+
+// 双向链表的随机快速排序
+// 课上没有讲，因为这是群里同学问的问题
+// 作为补充放在这，有需要的同学可以看看
+// 和课上讲的数组的经典快速排序在算法上没有区别
+// 但是coding需要更小心
+public class Code04_DoubleLinkedListQuickSort {
+
+	public static class Node {
+		public int value;
+		public Node last;
+		public Node next;
+
+		public Node(int v) {
+			value = v;
+		}
+	}
+
+	public static Node quickSort(Node h) {
+		if (h == null) {
+			return null;
+		}
+		int N = 0;
+		Node c = h;
+		Node e = null;
+		while (c != null) {
+			N++;
+			e = c;
+			c = c.next;
+		}
+		return process(h, e, N).h;
+	}
+
+	public static class HeadTail {
+		public Node h;
+		public Node t;
+
+		public HeadTail(Node head, Node tail) {
+			h = head;
+			t = tail;
+		}
+	}
+
+	// L...R是一个双向链表的头和尾,
+	// L的last指针指向null，R的next指针指向null
+	// 也就是说L的左边没有，R的右边也没节点
+	// 就是一个正常的双向链表，一共有N个节点
+	// 将这一段用随机快排的方式排好序
+	// 返回排好序之后的双向链表的头和尾(HeadTail)
+	public static HeadTail process(Node L, Node R, int N) {
+		if (L == null) {
+			return null;
+		}
+		if (L == R) {
+			return new HeadTail(L, R);
+		}
+		// L..R上不只一个节点
+		// 随机得到一个随机下标
+		int randomIndex = (int) (Math.random() * N);
+		// 根据随机下标得到随机节点
+		Node randomNode = L;
+		while (randomIndex-- != 0) {
+			randomNode = randomNode.next;
+		}
+		// 把随机节点从原来的环境里分离出来
+		// 比如 a(L) -> b -> c -> d(R), 如果randomNode = c，那么调整之后
+		// a(L) -> b -> d(R), c会被挖出来，randomNode = c
+		if (randomNode == L || randomNode == R) {
+			if (randomNode == L) {
+				L = randomNode.next;
+				L.last = null;
+			} else {
+				randomNode.last.next = null;
+			}
+		} else { // randomNode一定是中间的节点
+			randomNode.last.next = randomNode.next;
+			randomNode.next.last = randomNode.last;
+		}
+		randomNode.last = null;
+		randomNode.next = null;
+		Info info = partition(L, randomNode);
+		// <randomNode的部分去排序
+		HeadTail lht = process(info.lh, info.lt, info.ls);
+		// >randomNode的部分去排序
+		HeadTail rht = process(info.rh, info.rt, info.rs);
+		// 左部分排好序、右部分排好序
+		// 把它们串在一起
+		if (lht != null) {
+			lht.t.next = info.eh;
+			info.eh.last = lht.t;
+		}
+		if (rht != null) {
+			info.et.next = rht.h;
+			rht.h.last = info.et;
+		}
+		// 返回排好序之后总的头和总的尾
+		Node h = lht != null ? lht.h : info.eh;
+		Node t = rht != null ? rht.t : info.et;
+		return new HeadTail(h, t);
+	}
+
+	public static class Info {
+		public Node lh;
+		public Node lt;
+		public int ls;
+		public Node rh;
+		public Node rt;
+		public int rs;
+		public Node eh;
+		public Node et;
+
+		public Info(Node lH, Node lT, int lS, Node rH, Node rT, int rS, Node eH, Node eT) {
+			lh = lH;
+			lt = lT;
+			ls = lS;
+			rh = rH;
+			rt = rT;
+			rs = rS;
+			eh = eH;
+			et = eT;
+		}
+	}
+
+	// (L....一直到空)，是一个双向链表
+	// pivot是一个不在(L....一直到空)的独立节点，它作为划分值
+	// 根据荷兰国旗问题的划分方式，把(L....一直到空)划分成:
+	// <pivot 、 =pivot 、 >pivot 三个部分，然后把pivot融进=pivot的部分
+	// 比如 4(L)->6->7->1->5->0->9->null pivot=5(这个5和链表中的5，是不同的节点)
+	// 调整完成后:
+	// 4->1->0 小于的部分
+	// 5->5 等于的部分
+	// 6->7->9 大于的部分
+	// 三个部分是断开的
+	// 然后返回Info：
+	// 小于部分的头、尾、节点个数 : lh,lt,ls
+	// 大于部分的头、尾、节点个数 : rh,rt,rs
+	// 等于部分的头、尾 : eh,et
+	public static Info partition(Node L, Node pivot) {
+		Node lh = null;
+		Node lt = null;
+		int ls = 0;
+		Node rh = null;
+		Node rt = null;
+		int rs = 0;
+		Node eh = pivot;
+		Node et = pivot;
+		Node tmp = null;
+		while (L != null) {
+			tmp = L.next;
+			L.next = null;
+			L.last = null;
+			if (L.value < pivot.value) {
+				ls++;
+				if (lh == null) {
+					lh = L;
+					lt = L;
+				} else {
+					lt.next = L;
+					L.last = lt;
+					lt = L;
+				}
+			} else if (L.value > pivot.value) {
+				rs++;
+				if (rh == null) {
+					rh = L;
+					rt = L;
+				} else {
+					rt.next = L;
+					L.last = rt;
+					rt = L;
+				}
+			} else {
+				if (eh == null) {
+					eh = L;
+					et = L;
+				} else {
+					et.next = L;
+					L.last = et;
+					et = L;
+				}
+			}
+			L = tmp;
+		}
+		return new Info(lh, lt, ls, rh, rt, rs, eh, et);
+	}
+
+	// 为了测试
+	public static class NodeComp implements Comparator<Node> {
+
+		@Override
+		public int compare(Node o1, Node o2) {
+			return o1.value - o2.value;
+		}
+
+	}
+
+	// 为了测试
+	public static Node sort(Node head) {
+		if (head == null) {
+			return null;
+		}
+		ArrayList<Node> arr = new ArrayList<>();
+		while (head != null) {
+			arr.add(head);
+			head = head.next;
+		}
+		arr.sort(new NodeComp());
+		Node h = arr.get(0);
+		h.last = null;
+		Node p = h;
+		for (int i = 1; i < arr.size(); i++) {
+			Node c = arr.get(i);
+			p.next = c;
+			c.last = p;
+			c.next = null;
+			p = c;
+		}
+		return h;
+	}
+
+	// 为了测试
+	public static Node generateRandomDoubleLinkedList(int n, int v) {
+		if (n == 0) {
+			return null;
+		}
+		Node[] arr = new Node[n];
+		for (int i = 0; i < n; i++) {
+			arr[i] = new Node((int) (Math.random() * v));
+		}
+		Node head = arr[0];
+		Node pre = head;
+		for (int i = 1; i < n; i++) {
+			pre.next = arr[i];
+			arr[i].last = pre;
+			pre = arr[i];
+		}
+		return head;
+	}
+
+	// 为了测试
+	public static Node cloneDoubleLinkedList(Node head) {
+		if (head == null) {
+			return null;
+		}
+		Node h = new Node(head.value);
+		Node p = h;
+		head = head.next;
+		while (head != null) {
+			Node c = new Node(head.value);
+			p.next = c;
+			c.last = p;
+			p = c;
+			head = head.next;
+		}
+		return h;
+	}
+
+	// 为了测试
+	public static boolean equal(Node h1, Node h2) {
+		return doubleLinkedListToString(h1).equals(doubleLinkedListToString(h2));
+	}
+
+	// 为了测试
+	public static String doubleLinkedListToString(Node head) {
+		Node cur = head;
+		Node end = null;
+		StringBuilder builder = new StringBuilder();
+		while (cur != null) {
+			builder.append(cur.value + " ");
+			end = cur;
+			cur = cur.next;
+		}
+		builder.append("| ");
+		while (end != null) {
+			builder.append(end.value + " ");
+			end = end.last;
+		}
+		return builder.toString();
+	}
+
+	// 为了测试
+	public static void main(String[] args) {
+		int N = 500;
+		int V = 500;
+		int testTime = 10000;
+		System.out.println("测试开始");
+		for (int i = 0; i < testTime; i++) {
+			int size = (int) (Math.random() * N);
+			Node head1 = generateRandomDoubleLinkedList(size, V);
+			Node head2 = cloneDoubleLinkedList(head1);
+			Node sort1 = quickSort(head1);
+			Node sort2 = sort(head2);
+			if (!equal(sort1, sort2)) {
+				System.out.println("出错了!");
+				break;
+			}
+		}
+		System.out.println("测试结束");
+	}
+
+}