diff --git a/budd-common/src/main/java/io/github/ehlxr/algorithm/linkedlist/Leecode21.java b/budd-common/src/main/java/io/github/ehlxr/algorithm/linkedlist/Leecode21.java
new file mode 100644
index 0000000..49b0a38
--- /dev/null
+++ b/budd-common/src/main/java/io/github/ehlxr/algorithm/linkedlist/Leecode21.java
@@ -0,0 +1,122 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2020 xrv <xrg@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.algorithm.linkedlist;
+
+/**
+ * @author ehlxr
+ * @since 2022-04-15 08:41.
+ */
+public class Leecode21 {
+    public static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode() {
+        }
+
+        ListNode(int val) {
+            this.val = val;
+        }
+
+        ListNode(int val, ListNode next) {
+            this.val = val;
+            this.next = next;
+        }
+    }
+
+    public static void main(String[] args) {
+        ListNode list1 = new ListNode(1);
+        ListNode list2 = new ListNode(2);
+        ListNode list3 = new ListNode(4);
+        list1.next = list2;
+        list2.next = list3;
+        ListNode list4 = new ListNode(1);
+        ListNode list5 = new ListNode(3);
+        ListNode list6 = new ListNode(4);
+        list4.next = list5;
+        list5.next = list6;
+        ListNode list7 = mergeTwoLists(list1, list4);
+        while (list7 != null) {
+            System.out.println(list7.val);
+            list7 = list7.next;
+        }
+    }
+
+    public static ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        ListNode res = new ListNode();
+        ListNode tmp = res;
+
+        while (list1 != null || list2 != null) {
+            if (list1 == null) {
+                tmp.next = list2;
+                break;
+            }
+            if (list2 == null) {
+                tmp.next = list1;
+                break;
+            }
+            if (list1.val < list2.val) {
+                tmp.next = list1;
+                list1 = list1.next;
+            } else {
+                tmp.next = list2;
+                list2 = list2.next;
+            }
+            tmp = tmp.next;
+        }
+
+        return res.next;
+    }
+
+    public static ListNode  mergeTwoLists2(ListNode l1, ListNode l2) {
+        // 虚拟头结点
+        ListNode dummy = new ListNode(-1), p = dummy;
+        ListNode p1 = l1, p2 = l2;
+
+        while (p1 != null && p2 != null) {
+            // 比较 p1 和 p2 两个指针
+            // 将值较小的的节点接到 p 指针
+            if (p1.val > p2.val) {
+                p.next = p2;
+                p2 = p2.next;
+            } else {
+                p.next = p1;
+                p1 = p1.next;
+            }
+            // p 指针不断前进
+            p = p.next;
+        }
+
+        if (p1 != null) {
+            p.next = p1;
+        }
+
+        if (p2 != null) {
+            p.next = p2;
+        }
+
+        return dummy.next;
+    }
+}