From 43de941f2f0bef5a883d6bc4f66902fe9d4b23d2 Mon Sep 17 00:00:00 2001
From: Omar Boukli-Hacene <oboukli@users.noreply.github.com>
Date: Tue, 5 Sep 2023 13:21:47 +0200
Subject: [PATCH] Add palindromic number non-STL implementation

---
 CMakeLists.txt                             |  1 +
 benchmark/palindromic_number_benchmark.cpp | 42 ++++++++++++++++++++++
 include/forfun/palindromic_number.hpp      | 23 ++++++++++++
 src/palindromic_number.cpp                 |  8 +++++
 test/palindromic_number_test.cpp           |  3 +-
 5 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 benchmark/palindromic_number_benchmark.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0db0352..1213412 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -157,6 +157,7 @@ add_executable(
   "benchmark/first_missing_positive_benchmark.cpp"
   "benchmark/lru_cache_benchmark.cpp"
   "benchmark/palindrome_benchmark.cpp"
+  "benchmark/palindromic_number_benchmark.cpp"
 )
 target_link_libraries(
   benchmark
diff --git a/benchmark/palindromic_number_benchmark.cpp b/benchmark/palindromic_number_benchmark.cpp
new file mode 100644
index 0000000..053993f
--- /dev/null
+++ b/benchmark/palindromic_number_benchmark.cpp
@@ -0,0 +1,42 @@
+// Copyright (c) Omar Boukli-Hacene. All rights reserved.
+// Distributed under an MIT-style license that can be
+// found in the LICENSE file.
+
+// SPDX-License-Identifier: MIT
+
+#include <type_traits>
+
+#include <catch2/catch_test_macros.hpp>
+
+#include <nanobench.h>
+
+#include <nameof.hpp>
+
+#include "forfun/palindromic_number.hpp"
+
+inline constexpr int const p{1234554321};
+
+TEST_CASE(
+    "palindromic_number benchmarking", "[benchmark][palindromic_number]") {
+    static_assert(p >= 0 && p <= std::numeric_limits<decltype(p)>::max());
+
+    ankerl::nanobench::Bench()
+
+        .title("Palindromic number")
+
+        .run(
+            NAMEOF_RAW(forfun::palindromic_number::fast::is_palindrome).c_str(),
+            []() {
+                auto r{forfun::palindromic_number::fast::is_palindrome(p)};
+                ankerl::nanobench::doNotOptimizeAway(r);
+            })
+
+        .run(
+            NAMEOF_RAW(forfun::palindromic_number::stl::is_palindrome).c_str(),
+            []() {
+                auto r{forfun::palindromic_number::stl::is_palindrome(p)};
+                ankerl::nanobench::doNotOptimizeAway(r);
+            })
+
+        ;
+}
diff --git a/include/forfun/palindromic_number.hpp b/include/forfun/palindromic_number.hpp
index daa48be..5b80bfc 100644
--- a/include/forfun/palindromic_number.hpp
+++ b/include/forfun/palindromic_number.hpp
@@ -10,6 +10,29 @@
 #ifndef FORFUN_PALINDROMIC_NUMBER_HPP_
 #define FORFUN_PALINDROMIC_NUMBER_HPP_
 
+namespace forfun::palindromic_number {
+
+namespace fast {
+
+[[nodiscard]] constexpr bool is_palindrome(int const n) noexcept {
+    int nn{0};
+    int d{n};
+    while (d > 0) {
+        nn = (nn * 10) + d % 10;
+        d /= 10;
+    }
+
+    return n == nn;
+}
+
+} // namespace fast
+
+namespace stl {
+
 [[nodiscard]] bool is_palindrome(int const n) noexcept;
 
+} // namespace stl
+
+} // namespace forfun::palindromic_number
+
 #endif // FORFUN_PALINDROMIC_NUMBER_HPP_
diff --git a/src/palindromic_number.cpp b/src/palindromic_number.cpp
index 037b838..8cc91f4 100644
--- a/src/palindromic_number.cpp
+++ b/src/palindromic_number.cpp
@@ -8,6 +8,10 @@
 
 #include <cstdlib>
 
+namespace forfun::palindromic_number {
+
+namespace stl {
+
 [[nodiscard]] bool is_palindrome(int const n) noexcept {
     int nn{0};
     std::div_t d{.quot = n, .rem = 0};
@@ -18,3 +22,7 @@
 
     return n == nn;
 }
+
+} // namespace stl
+
+} // namespace forfun::palindromic_number
diff --git a/test/palindromic_number_test.cpp b/test/palindromic_number_test.cpp
index 113eadf..6c54130 100644
--- a/test/palindromic_number_test.cpp
+++ b/test/palindromic_number_test.cpp
@@ -12,7 +12,8 @@
 
 TEMPLATE_TEST_CASE_SIG(
     "palindromic_number", "", ((auto sut), sut),
-    (is_palindrome)) {
+    (forfun::palindromic_number::fast::is_palindrome),
+    (forfun::palindromic_number::stl::is_palindrome)) {
     SECTION("Palindromic numbers") {
         GIVEN("a palindromic number") {
             auto const [palindromic_number]{GENERATE(table<int>({