diff --git a/.vscode/settings.json b/.vscode/settings.json
index ee8c403..16c52fb 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -68,6 +68,26 @@
         "cinttypes": "cpp",
         "typeindex": "cpp",
         "typeinfo": "cpp",
-        "variant": "cpp"
+        "variant": "cpp",
+        "__bit_reference": "cpp",
+        "__config": "cpp",
+        "__debug": "cpp",
+        "__errc": "cpp",
+        "__functional_base": "cpp",
+        "__hash_table": "cpp",
+        "__locale": "cpp",
+        "__mutex_base": "cpp",
+        "__node_handle": "cpp",
+        "__nullptr": "cpp",
+        "__split_buffer": "cpp",
+        "__std_stream": "cpp",
+        "__string": "cpp",
+        "__threading_support": "cpp",
+        "__tree": "cpp",
+        "__tuple": "cpp",
+        "ios": "cpp",
+        "locale": "cpp",
+        "queue": "cpp",
+        "stack": "cpp"
     }
 }
\ No newline at end of file
diff --git a/0024.h b/0024.h
new file mode 100644
index 0000000..3206e67
--- /dev/null
+++ b/0024.h
@@ -0,0 +1,28 @@
+#include "common.h"
+
+namespace s0024 {
+    //  Definition for singly-linked list.
+    struct ListNode {
+        int val;
+        ListNode *next;
+        ListNode() : val(0), next(nullptr) {}
+        ListNode(int x) : val(x), next(nullptr) {}
+        ListNode(int x, ListNode *next) : val(x), next(next) {}
+    };
+    class Solution {
+    public:
+        ListNode* swapPairs(ListNode* head) {
+            ListNode* dummyHead = new ListNode(0, head);
+            ListNode* cur = dummyHead;
+            while (cur->next != nullptr && cur->next->next != nullptr) {
+                ListNode* tmp = cur->next;
+                ListNode* tmp1 = cur->next->next->next;
+                cur->next = cur->next->next;
+                cur->next->next = tmp;
+                cur->next->next->next = tmp1;
+                cur = cur->next->next;
+            }
+            return dummyHead->next;
+        }
+    };
+}
\ No newline at end of file
diff --git a/test.cc b/test.cc
index 4f0cc50..4560439 100644
--- a/test.cc
+++ b/test.cc
@@ -1,10 +1,33 @@
 #include "0001.h"
+#include "0024.h"
 #include <gtest/gtest.h>
 
-
-TEST(S001, Normal) {
+TEST(S0001, Normal) {
     s0001::Solution s;
-    std::vector<int> v = {1,2,3};
-    // std::vector<int> r = {0,1};
-    EXPECT_EQ(std::vector<int>({0,1}), s.twoSum(v, 3));
-}
\ No newline at end of file
+    std::vector<int> v1 = {1,2,3};
+    std::vector<int> v2 = {1,1,1};
+    EXPECT_EQ(std::vector({0,1}), s.twoSum(v1, 3));
+    EXPECT_EQ(std::vector({0,1}), s.twoSum(v2, 2));
+}
+
+s0024::ListNode* createList(vector<int> v) {
+    s0024::ListNode* head = new s0024::ListNode(v[0]);
+    s0024::ListNode* tmp = head;
+    for (int i=1; i<v.size(); i++) {
+        s0024::ListNode* node = new s0024::ListNode(v[i]);
+        tmp->next = node;
+        tmp = tmp->next;
+    }
+    return head;
+}
+
+TEST(S0024, Normal) {
+    s0024::Solution s;
+    s0024::ListNode* t1 = createList(vector<int>{1,2,3,4});
+    s0024::ListNode* r = s.swapPairs(t1);
+    vector<int> exp({2,1,4,3});
+    for (int i=0; i<exp.size(); i++) {
+        EXPECT_EQ(exp[i], r->val);
+        r = r->next;
+    }
+}