diff --git a/README.md b/README.md
index 154648e..23f3742 100644
--- a/README.md
+++ b/README.md
@@ -687,6 +687,10 @@ C++标准库提供的数据结构实在是太多了，参考[C++标准库头文
 
 ### 其它
 
+- [构造有效字符串的最少插入数](src/other/minimum_additions_to_make_valid_string.cpp)  [Stack, Greedy, String, Dynamic Programming]
+
+  - LeetCode 2645. 构造有效字符串的最少插入数 <https://leetcode.cn/problems/minimum-additions-to-make-valid-string>
+
 - [最小体力消耗路径](src/search/path_with_minimum_effort.cpp)  [深度优先搜索, 广度优先搜索, 并查集, 数组, 二分查找, 矩阵, 堆（优先队列）]
 
   - LeetCode 1631. 最小体力消耗路径 <https://leetcode.cn/problems/path-with-minimum-effort>
diff --git a/images/other/minimum_additions_to_make_valid_string.jpeg b/images/other/minimum_additions_to_make_valid_string.jpeg
new file mode 100644
index 0000000..bd42fb8
Binary files /dev/null and b/images/other/minimum_additions_to_make_valid_string.jpeg differ
diff --git a/src/other/minimum_additions_to_make_valid_string.cpp b/src/other/minimum_additions_to_make_valid_string.cpp
new file mode 100644
index 0000000..e2f32fc
--- /dev/null
+++ b/src/other/minimum_additions_to_make_valid_string.cpp
@@ -0,0 +1,18 @@
+// 构造有效字符串的最少插入数
+// https://leetcode.cn/problems/minimum-additions-to-make-valid-string
+// INLINE  ../../images/other/minimum_additions_to_make_valid_string.jpeg
+
+#include <headers.hpp>
+
+class Solution {
+public:
+  int addMinimum(string word) {
+    int n = word.size(), cnt = 1;
+    for (int i = 1; i < n; i++) {
+      if (word[i] <= word[i - 1]) {
+        cnt++;
+      }
+    }
+    return cnt * 3 - n;
+  }
+};
\ No newline at end of file
diff --git a/test/lib/lib_test.cpp b/test/lib/lib_test.cpp
index c11c5f9..d966976 100644
--- a/test/lib/lib_test.cpp
+++ b/test/lib/lib_test.cpp
@@ -1,4 +1,4 @@
-// 执行编译时间：2024-01-10 21:59:48
+// 执行编译时间：2024-01-11 11:49:55
 #include <gtest/gtest.h>
 #include <lib.hpp>
 
diff --git a/test/other/minimum_additions_to_make_valid_string_test.cpp b/test/other/minimum_additions_to_make_valid_string_test.cpp
new file mode 100644
index 0000000..d63c4d7
--- /dev/null
+++ b/test/other/minimum_additions_to_make_valid_string_test.cpp
@@ -0,0 +1,28 @@
+#include <other/minimum_additions_to_make_valid_string.cpp>
+
+TEST(构造有效字符串的最少插入数, addMinimum) {
+  Solution solution;
+  // 示例 1：
+  // 输入：word = "b"
+  // 输出：2
+  // 解释：在 "b" 之前插入 "a" ，在 "b" 之后插入 "c" 可以得到有效字符串 "abc" 。
+  string word = "b";
+  int expected = 2;
+  EXPECT_EQ(solution.addMinimum(word), expected);
+
+  // 示例 2：
+  // 输入：word = "aaa"
+  // 输出：6
+  // 解释：在每个 "a" 之后依次插入 "b" 和 "c" 可以得到有效字符串 "abcabcabc" 。
+  word = "aaa";
+  expected = 6;
+  EXPECT_EQ(solution.addMinimum(word), expected);
+
+  // 示例 3：
+  // 输入：word = "abc"
+  // 输出：0
+  // 解释：word 已经是有效字符串，不需要进行修改。
+  word = "abc";
+  expected = 0;
+  EXPECT_EQ(solution.addMinimum(word), expected);
+}