commit f5e7baa1bdde00a025432c8c3bf8bbc26f7cb364
Author: Wong Ding Feng <dingfengwong@gmail.com>
Date:   Sat Mar 14 23:25:02 2026 +0800

    Initial commit: Modular Clang C++ Nix environment and problem files

diff --git a/Problems b/Problems
new file mode 100644
index 0000000..eaca1aa
Binary files /dev/null and b/Problems differ
diff --git a/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.cpp b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.cpp
new file mode 100644
index 0000000..8988546
--- /dev/null
+++ b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.cpp
@@ -0,0 +1,5 @@
+class Solution {
+public:
+    string getHappyString(int n, int k) {
+    }
+};
diff --git a/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.rs b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.rs
new file mode 100644
index 0000000..cfe59ae
--- /dev/null
+++ b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.rs
@@ -0,0 +1,5 @@
+impl Solution {
+    pub fn get_happy_string(n: i32, k: i32) -> String {
+        
+    }
+}
diff --git a/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.tests.dat b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.tests.dat
new file mode 100644
index 0000000..b642cbc
--- /dev/null
+++ b/code/1415.the-k-th-lexicographical-string-of-all-happy-strings-of-length-n.tests.dat
@@ -0,0 +1,6 @@
+1
+3
+1
+4
+3
+9
\ No newline at end of file
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..9b54eed
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,34 @@
+{
+  description: "A modular Clang C++ development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, treefmt-nix }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          config.allowUnfree = true;
+        };
+        
+        # Configuration for LLVM/Clang version
+        # Change this to "16", "17", "18", or "19" to switch versions
+        llvmVersion = "18";
+        
+        nixLib = import ./nix {
+          inherit pkgs treefmt-nix llvmVersion;
+        };
+      in
+      {
+        devShells.default = nixLib.devShell;
+        formatter = nixLib.formatter;
+      }
+    );
+}
diff --git a/leetcode.toml b/leetcode.toml
new file mode 100644
index 0000000..53ad43b
--- /dev/null
+++ b/leetcode.toml
@@ -0,0 +1,15 @@
+[code]
+editor = "emacsclient"
+test = true
+lang = "cpp"
+
+[cookies]
+csrf = "r8aszHnQmx8ihvyyf6IiinGc3oO84R8G"
+session = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.fBFD0da7kfN9EcNCqpHtHBivJuepwQRS7AVwmH-LX4Q"
+site = "leetcode.com"
+
+[storage]
+cache = "Problems"
+code = "code"
+root = "~/.leetcode"
+scripts = "scripts"
diff --git a/nix/default.nix b/nix/default.nix
new file mode 100644
index 0000000..00f91aa
--- /dev/null
+++ b/nix/default.nix
@@ -0,0 +1,9 @@
+{ pkgs, treefmt-nix, llvmVersion }:
+let
+  treefmt = import ./treefmt.nix { inherit pkgs treefmt-nix; };
+  devShell = import ./devshells/default.nix { inherit pkgs llvmVersion; };
+in
+{
+  inherit devShell;
+  formatter = treefmt.config.build.wrapper;
+}
diff --git a/nix/devshells/default.nix b/nix/devshells/default.nix
new file mode 100644
index 0000000..67a60b6
--- /dev/null
+++ b/nix/devshells/default.nix
@@ -0,0 +1,38 @@
+{ pkgs, llvmVersion }:
+let
+  # Select the correct LLVM/Clang version
+  llvmPackages = pkgs."llvmPackages_${llvmVersion}";
+in
+pkgs.mkShell {
+  name = "clang-cpp-shell";
+
+  # Native dependencies (e.g., compilers, build tools)
+  nativeBuildInputs = with pkgs; [
+    # Compiler and core tools
+    llvmPackages.clang
+    llvmPackages.lld
+    llvmPackages.bintools
+    
+    # Language-specific tools
+    llvmPackages.clang-tools # Includes clang-format, clang-tidy
+    cmake
+    ninja
+    gdb
+    valgrind
+    nixpkgs-fmt
+  ];
+
+  # Runtime dependencies (e.g., shared libraries)
+  buildInputs = with pkgs; [
+    # Common libraries (example)
+    libcxx
+    boost
+  ];
+
+  # Environment variables
+  shellHook = ''
+    export CC=clang
+    export CXX=clang++
+    echo "Clang version: $(${llvmPackages.clang}/bin/clang --version | head -n 1)"
+  '';
+}
diff --git a/nix/treefmt.nix b/nix/treefmt.nix
new file mode 100644
index 0000000..054c1bf
--- /dev/null
+++ b/nix/treefmt.nix
@@ -0,0 +1,16 @@
+{ pkgs, treefmt-nix }:
+treefmt-nix.lib.evalModule pkgs {
+  projectRootFile = "flake.nix";
+  
+  # Configure individual formatters
+  programs = {
+    # Nix formatter
+    nixpkgs-fmt.enable = true;
+    
+    # C++ formatter
+    clang-format.enable = true;
+  };
+
+  # Optional settings
+  settings.formatter.clang-format.includes = [ "*.cpp" "*.h" "*.hpp" "*.c" ];
+}