diff --git a/leetcode/0392/solution.hpp b/leetcode/0392/solution.hpp
index 92950f0..f052937 100644
--- a/leetcode/0392/solution.hpp
+++ b/leetcode/0392/solution.hpp
@@ -1,19 +1,18 @@
 #include <string>
 
-class Solution {
-public:
-    bool isSubsequence(std::string s, std::string t) {
+// 方法1：双指针
+struct Solution {
+    static bool isSubsequence(const std::string &s, const std::string &t) {
+        std::size_t ss{s.size()}, ts{t.size()};
         if (s.size() > t.size()) {
             return false;
         }
-        std::size_t pos{0};
-        for (char ch : s) {
-            pos = t.find(ch, pos);
-            if (pos == t.npos) {
-                return false;
+        std::size_t si{0};
+        for (std::size_t ti{0}; si < ss && ti < ts; ++ti) {
+            if (s[si] == t[ti]) {
+                ++si;
             }
-            ++pos;
         }
-        return true;
+        return si == ss;
     }
 };
diff --git a/leetcode/0392/test.cpp b/leetcode/0392/test.cpp
index 47a1f06..4bb8934 100644
--- a/leetcode/0392/test.cpp
+++ b/leetcode/0392/test.cpp
@@ -41,4 +41,5 @@ void Expect(const TestCase &tc) {
 
 TEST_Y(LeetCode392, Example1);
 TEST_Y(LeetCode392, Example2);
+TEST_Y(LeetCode392, Regression1);
 } // namespace
diff --git a/leetcode/0392/test_suite.yaml b/leetcode/0392/test_suite.yaml
index 795a751..64f65bb 100644
--- a/leetcode/0392/test_suite.yaml
+++ b/leetcode/0392/test_suite.yaml
@@ -9,3 +9,9 @@ example2:
     s: "axc"
     t: "ahbgdc"
   expected: false
+
+regression1:
+  input:
+    s: "abc"
+    t: ""
+  expected: false
diff --git a/leetcode/2011/solution.hpp b/leetcode/2011/solution.hpp
index b296321..88906e6 100644
--- a/leetcode/2011/solution.hpp
+++ b/leetcode/2011/solution.hpp
@@ -4,8 +4,7 @@
 
 // 方法1：模拟
 namespace approach1 {
-class Solution {
-public:
+struct Solution {
     static int finalValueAfterOperations(const std::vector<std::string> &operations) {
         int res{0};
         for (const auto &op : operations) {
@@ -20,10 +19,9 @@ class Solution {
 };
 } // namespace approach1
 
-// 方法2：计数
+// 方法2：计数 + 数学推导
 namespace approach2 {
-class Solution {
-public:
+struct Solution {
     static int finalValueAfterOperations(const std::vector<std::string> &operations) {
         auto isInc{[](const std::string &op) { return op[1] == '+'; }};
         return 2 * std::ranges::count_if(operations, isInc) - operations.size();