diff --git a/src/klotski/common_code/common_code.cc b/src/klotski/common_code/common_code.cc
index 1a733f0..573a783 100644
--- a/src/klotski/common_code/common_code.cc
+++ b/src/klotski/common_code/common_code.cc
@@ -2,47 +2,59 @@
 #include "common.h"
 #include "common_code.h"
 
-using klotski::CommonCode;
+namespace std {
+    template<>
+    struct hash<klotski::CommonCode> {
+        std::size_t operator()(const klotski::CommonCode &c) const {
+            return std::hash<uint64_t>()(c.unwrap());
+        }
+    };
 
-uint64_t CommonCode::unwrap() const {
-    return code; // raw uint64_t code
+    template<>
+    struct equal_to<klotski::CommonCode> {
+        bool operator()(const klotski::CommonCode &c1, const klotski::CommonCode &c2) const {
+            return c1.unwrap() == c2.unwrap();
+        }
+    };
 }
 
-bool CommonCode::valid() const {
-    return CommonCode::check(code);
-}
+namespace klotski {
+    bool CommonCode::operator==(const CommonCode &common_code) const {
+        return this->code == common_code.code;
+    }
 
-CommonCode CommonCode::create(uint64_t common_code) {
-    return CommonCode(common_code); // create from uint64_t
+    std::ostream& operator<<(std::ostream &out, const CommonCode &self) {
+        char str[10];
+        sprintf(str, "%09lX", self.code);
+        out << str;
+        return out;
+    }
 }
 
-CommonCode CommonCode::unsafe_create(uint64_t common_code) { // create without check
-    auto common = CommonCode(); // init directly
-    common.code = common_code;
-    return common;
-}
+namespace klotski {
+    bool CommonCode::valid() const {
+        return CommonCode::check(code);
+    }
 
-CommonCode::CommonCode(uint64_t common_code) {
-    if (!CommonCode::check(common_code)) { // check input common code
-        throw std::invalid_argument("invalid common code");
+    CommonCode CommonCode::create(uint64_t common_code) {
+        return CommonCode(common_code); // create from uint64_t
     }
-    code = common_code;
-}
 
-bool CommonCode::operator==(const CommonCode &common_code) const {
-    return this->code == common_code.code;
-}
+    CommonCode CommonCode::unsafe_create(uint64_t common_code) { // create without check
+        auto tmp = CommonCode(); // init directly
+        tmp.code = common_code;
+        return tmp;
+    }
 
-namespace klotski {
-    std::ostream &operator<<(std::ostream &out, const CommonCode &self) {
-        char str[10];
-        sprintf(str, "%09lX", self.code);
-        out << str;
-        return out;
+    CommonCode::CommonCode(uint64_t common_code) {
+        if (!CommonCode::check(common_code)) { // check input common code
+            throw std::invalid_argument("invalid common code");
+        }
+        code = common_code;
     }
 }
 
-bool CommonCode::check(uint64_t common_code) { // whether common code is valid
+bool klotski::CommonCode::check(uint64_t common_code) { // whether common code is valid
     ///   M_1x1     M_1x2     M_2x1     M_2x2
     ///  1 0 0 0   1 1 0 0   1 0 0 0   1 1 0 0
     ///  0 0 0 0   0 0 0 0   1 0 0 0   1 1 0 0
diff --git a/src/klotski/common_code/common_code.h b/src/klotski/common_code/common_code.h
index 9c7cb84..bfb415a 100644
--- a/src/klotski/common_code/common_code.h
+++ b/src/klotski/common_code/common_code.h
@@ -13,19 +13,19 @@ namespace klotski {
 
     class CommonCode {
     public:
-        bool valid() const;
+        inline bool valid() const;
         static bool check(uint64_t common_code);
 
         /// Operators of CommonCode
-        explicit operator uint64_t() const { return code; }
+        constexpr operator uint64_t() const { return code; }
         bool operator==(const CommonCode &common_code) const;
         friend std::ostream& operator<<(std::ostream &out, const CommonCode &self);
 
         /// Export functions
-        uint64_t unwrap() const;
         RawCode to_raw_code() const;
         ShortCode to_short_code() const;
         std::string to_string(bool shorten = false) const;
+        constexpr uint64_t unwrap() const { return code; }
 
         /// CommonCode constructors
         explicit CommonCode(uint64_t common_code);
diff --git a/src/klotski/raw_code/raw_code.cc b/src/klotski/raw_code/raw_code.cc
index 9fb015e..fbb4ef2 100644
--- a/src/klotski/raw_code/raw_code.cc
+++ b/src/klotski/raw_code/raw_code.cc
@@ -2,43 +2,32 @@
 #include "common.h"
 #include "raw_code.h"
 
-using klotski::RawCode;
-
-uint64_t RawCode::unwrap() const {
-    return code; // raw uint64_t code
-}
-
-bool RawCode::valid() const {
-    return RawCode::check(code);
-}
-
-RawCode RawCode::create(uint64_t raw_code) {
-    return RawCode(raw_code);
-}
+namespace std {
+    template<>
+    struct hash<klotski::RawCode> {
+        std::size_t operator()(const klotski::RawCode &c) const {
+            return std::hash<uint64_t>()(c.unwrap());
+        }
+    };
 
-RawCode RawCode::unsafe_create(uint64_t raw_code) { // create without check
-    auto raw = RawCode(); // init directly
-    raw.code = raw_code;
-    return raw;
+    template<>
+    struct equal_to<klotski::RawCode> {
+        bool operator()(const klotski::RawCode &c1, const klotski::RawCode &c2) const {
+            return c1.unwrap() == c2.unwrap();
+        }
+    };
 }
 
-RawCode::RawCode(uint64_t raw_code) {
-    if (!RawCode::check(raw_code)) { // check input raw code
-        throw std::invalid_argument("invalid raw code");
+namespace klotski {
+    bool RawCode::operator==(const RawCode &raw_code) const {
+        return this->code == raw_code.code;
     }
-    code = raw_code;
-}
-
-bool RawCode::operator==(const RawCode &raw_code) const {
-    return this->code == raw_code.code;
-}
 
-namespace klotski {
-    std::ostream &operator<<(std::ostream &out, const RawCode &self) {
+    std::ostream& operator<<(std::ostream &out, const RawCode &self) {
         char code[16];
         char dump_map[] = {
-                /// 0x0  1x2  2x1  1x1  2x2  b101 b110 fill
-                '.', '~', '|', '*', '@', '?', '?', '+'
+            /// 0x0  1x2  2x1  1x1  2x2  b101 b110 fill
+            '.', '~', '|', '*', '@', '?', '?', '+'
         };
         sprintf(code, "%015lX", self.code); // code length -> 15
         out << code << '\n';
@@ -50,7 +39,30 @@ namespace klotski {
     }
 }
 
-bool RawCode::check(uint64_t raw_code) { // check whether raw code is valid
+namespace klotski {
+    bool RawCode::valid() const {
+        return RawCode::check(code);
+    }
+
+    RawCode RawCode::create(uint64_t raw_code) {
+        return RawCode(raw_code);
+    }
+
+    RawCode RawCode::unsafe_create(uint64_t raw_code) { // create without check
+        auto tmp = RawCode(); // init directly
+        tmp.code = raw_code;
+        return tmp;
+    }
+
+    RawCode::RawCode(uint64_t raw_code) {
+        if (!RawCode::check(raw_code)) { // check input raw code
+            throw std::invalid_argument("invalid raw code");
+        }
+        code = raw_code;
+    }
+}
+
+bool klotski::RawCode::check(uint64_t raw_code) { // check whether raw code is valid
     ///     MASK_1x2          MASK_2x1         MASK_2x2
     ///  000 100 000 000   000 000 000 000  000 100 000 000
     ///  000 000 000 000   100 000 000 000  100 100 000 000
diff --git a/src/klotski/raw_code/raw_code.h b/src/klotski/raw_code/raw_code.h
index 67b1ead..9502c9a 100644
--- a/src/klotski/raw_code/raw_code.h
+++ b/src/klotski/raw_code/raw_code.h
@@ -45,17 +45,17 @@ namespace klotski {
 
     class RawCode {
     public:
-        bool valid() const;
+        inline bool valid() const;
         static bool check(uint64_t raw_code);
 
         /// Operators of RawCode
         bool operator==(const RawCode &raw_code) const;
-        explicit operator uint64_t() const { return code; }
+        constexpr operator uint64_t() const { return code; }
         friend std::ostream& operator<<(std::ostream &out, const RawCode &self);
 
         /// Export functions
-        uint64_t unwrap() const;
         CommonCode to_common_code() const;
+        constexpr uint64_t unwrap() const { return code; }
 
         /// RawCode constructors
         explicit RawCode(uint64_t raw_code);
diff --git a/src/klotski/short_code/short_code.cc b/src/klotski/short_code/short_code.cc
index 2db9273..8389945 100644
--- a/src/klotski/short_code/short_code.cc
+++ b/src/klotski/short_code/short_code.cc
@@ -1,42 +1,62 @@
 #include "all_cases.h"
 #include "short_code.h"
 
-using klotski::ShortCode;
+namespace std {
+    template<>
+    struct hash<klotski::ShortCode> {
+        std::size_t operator()(const klotski::ShortCode &c) const {
+            return std::hash<uint64_t>()(c.unwrap());
+        }
+    };
 
-uint32_t ShortCode::unwrap() const {
-    return code; // raw uint32_t code
+    template<>
+    struct equal_to<klotski::ShortCode> {
+        bool operator()(const klotski::ShortCode &c1, const klotski::ShortCode &c2) const {
+            return c1.unwrap() == c2.unwrap();
+        }
+    };
 }
 
-bool ShortCode::valid() const {
-    return ShortCode::check(code);
-}
+namespace klotski {
+    bool ShortCode::operator==(const ShortCode &short_code) const {
+        return this->code == short_code.code;
+    }
 
-ShortCode ShortCode::create(uint32_t short_code) {
-    return ShortCode(short_code);
+    std::ostream &operator<<(std::ostream &out, const ShortCode &self) {
+        out << self.to_string() << "(" << self.code << ")"; // short code info
+        return out;
+    }
 }
 
-ShortCode::ShortCode(uint32_t short_code) {
-    if (!ShortCode::check(short_code)) { // check input short code
-        throw std::invalid_argument("invalid short code");
+namespace klotski {
+    bool ShortCode::valid() const {
+        return ShortCode::check(code);
     }
-    code = short_code;
-}
 
-bool ShortCode::check(uint32_t short_code) {
-    return short_code < SHORT_CODE_LIMIT; // 0 ~ (SHORT_CODE_LIMIT - 1)
-}
+    ShortCode ShortCode::create(uint32_t short_code) {
+        return ShortCode(short_code);
+    }
 
-bool ShortCode::operator==(const ShortCode &short_code) const {
-    return this->code == short_code.code;
-}
+    ShortCode ShortCode::unsafe_create(uint32_t short_code) { // create without check
+        auto tmp = ShortCode(); // init directly
+        tmp.code = short_code;
+        return tmp;
+    }
 
-namespace klotski {
-    std::ostream &operator<<(std::ostream &out, const ShortCode &self) {
-        out << self.to_string() << "(" << self.code << ")"; // short code info
-        return out;
+    ShortCode::ShortCode(uint32_t short_code) {
+        if (!ShortCode::check(short_code)) { // check input short code
+            throw std::invalid_argument("invalid short code");
+        }
+        code = short_code;
     }
 }
 
+bool klotski::ShortCode::check(uint32_t short_code) {
+    return short_code < SHORT_CODE_LIMIT; // 0 ~ (SHORT_CODE_LIMIT - 1)
+}
+
+using klotski::ShortCode;
+
 bool ShortCode::fast_mode_available = false;
 bool ShortCode::normal_mode_available = false;
 
diff --git a/src/klotski/short_code/short_code.h b/src/klotski/short_code/short_code.h
index 9014e49..44ba4cd 100644
--- a/src/klotski/short_code/short_code.h
+++ b/src/klotski/short_code/short_code.h
@@ -13,19 +13,19 @@ namespace klotski {
     public:
         enum Mode {NORMAL, FAST};
 
-        bool valid() const;
+        inline bool valid() const;
         static void speed_up(enum Mode mode);
         static bool check(uint32_t short_code);
 
         /// Operators of ShortCode
-        explicit operator uint32_t() const { return code; }
+        constexpr operator uint32_t() const { return code; }
         bool operator==(const ShortCode &short_code) const;
         friend std::ostream& operator<<(std::ostream &out, const ShortCode &self);
 
         /// Export functions
-        uint32_t unwrap() const;
         std::string to_string() const;
         CommonCode to_common_code() const;
+        constexpr uint32_t unwrap() const { return code; }
 
         /// ShortCode constructors
         explicit ShortCode(uint32_t short_code);
@@ -38,6 +38,7 @@ namespace klotski {
 
         /// Rust-style initialization
         static ShortCode create(uint32_t short_code);
+        static ShortCode unsafe_create(uint32_t short_code);
         static ShortCode from_string(const std::string &short_code);
 
         static ShortCode from_common_code(uint64_t common_code);
@@ -50,6 +51,7 @@ namespace klotski {
         static bool normal_mode_available;
         static const uint32_t SHORT_CODE_LIMIT = 29334498;
 
+        ShortCode() = default; // unsafe initialize
         static enum Mode mode();
         static uint64_t fast_decode(uint32_t short_code);
         static uint32_t fast_encode(uint64_t common_code);