diff --git a/all_cases/CMakeLists.txt b/all_cases/CMakeLists.txt
index bb5c16d..a7791b1 100644
--- a/all_cases/CMakeLists.txt
+++ b/all_cases/CMakeLists.txt
@@ -1,4 +1,4 @@
 cmake_minimum_required(VERSION 3.0)
 set(CMAKE_CXX_STANDARD 14)
 
-add_executable(klotski main.cc)
+add_executable(klotski all_cases.cc short_code.cc)
diff --git a/all_cases/main.cc b/all_cases/all_cases.cc
similarity index 90%
rename from all_cases/main.cc
rename to all_cases/all_cases.cc
index 740685c..2a19a29 100644
--- a/all_cases/main.cc
+++ b/all_cases/all_cases.cc
@@ -143,29 +143,3 @@ void AllCases::find_all_cases() { // find all valid cases
         }
     }
 }
-
-int main() {
-    auto a = AllCases();
-
-//    std::cout << "basic: " << a.basic_ranges.size() << std::endl;
-//    std::cout << std::endl;
-//
-//    int sum = 0;
-//    a.find_all_cases();
-//    for (auto &all_case : a.all_cases) {
-//        sum += (int)all_case.size();
-//        std::cout << all_case.size() << std::endl;
-//    }
-//
-//    std::cout << std::endl;
-//    std::cout << "sum: " << sum << std::endl;
-
-    a.find_all_cases();
-    for (int n = 0; n < 16; ++n) {
-        for (auto &range : a.all_cases[n]) {
-            printf("%X%08X\n", n, range);
-        }
-    }
-
-    return 0;
-}
diff --git a/all_cases/short_code.cc b/all_cases/short_code.cc
new file mode 100644
index 0000000..3081834
--- /dev/null
+++ b/all_cases/short_code.cc
@@ -0,0 +1,61 @@
+#include <iostream>
+#include <algorithm>
+#include "all_cases.h"
+
+const uint32_t ALL_CASES_NUMBER = 29334498;
+
+std::string code_to_string(uint32_t short_code) {
+    if (short_code >= ALL_CASES_NUMBER) {
+        throw std::range_error("short code out of range");
+    }
+    std::string result(5, '\0'); // short code length 5
+    for (int i = 0; i < 5; ++i) {
+        uint8_t bit = short_code % 36;
+        short_code = (short_code - bit) / 36;
+        if (bit < 10) {
+            result[4 - i] = char(bit + 48); // 0 ~ 9
+        } else {
+            result[4 - i] = char(bit + 55); // A ~ Z
+        }
+    }
+    return result;
+}
+
+uint32_t code_from_string(const std::string &short_code) {
+    if (short_code.length() != 5) {
+        throw std::runtime_error("invalid short code");
+    }
+    uint32_t result = 0;
+    for (auto &bit : short_code) {
+        result *= 36;
+        if (bit >= '0' && bit <= '9') {
+            result += bit - 48; // 0 ~ 9
+        } else if (bit >= 'A' && bit <= 'Z') {
+            result += bit - 55; // A ~ Z
+        } else if (bit >= 'a' && bit <= 'z') {
+            result += bit - 87; // a ~ z
+        } else {
+            throw std::runtime_error("invalid short code");
+        }
+    }
+    if (result >= ALL_CASES_NUMBER) {
+        throw std::range_error("short code out of range");
+    }
+    return result;
+}
+
+int main() {
+
+//    auto a = AllCases();
+//    a.find_all_cases();
+//    int sum = 0;
+//    for (auto &all_case : a.all_cases) {
+//        sum += (int)all_case.size();
+//    }
+//    std::cout << sum << std::endl;
+
+    std::cout << code_to_string(14323231) << std::endl;
+    std::cout << code_from_string("8IzVj") << std::endl;
+
+    return 0;
+}