add 5 solution.

src/5/solution.hpp

@@ -0,0 +1,21 @@
+#include <string>
+#include <vector>
+
+class Solution {
+public:
+  std::string longestPalindrome(std::string s) {
+    const auto n = s.size();
+    s.insert(0, "-");
+
+    std::vector<int> dp(n, 1);
+    dp[0] = 0;
+
+    for (int i = 0; i < n; ++i) {
+      for (int j = i + 1; j < n; ++j) {
+
+      }
+    }
+
+    return {};
+  }
+};

tests/5/CMakeLists.txt

@@ -0,0 +1,37 @@
+cmake_minimum_required(VERSION 3.10)
+project(dp_solution_pipeline)
+
+set(CMAKE_CXX_STANDARD 17)
+
+set(PROBLEM_NAME 5)
+
+include(FetchContent)
+FetchContent_Declare(
+        googletest
+        URL https://github.com/google/googletest/archive/03597a01ee50ed33e9dfd640b249b4be3799d395.zip
+)
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+
+set(SRC_ROOT_PATH ${ROOT_PATH}/src)
+set(SRC_PATH ${SRC_ROOT_PATH}/${PROBLEM_NAME})
+set(TESTS_PATH ${ROOT_PATH}/tests/${PROBLEM_NAME})
+
+include_directories(
+        ${SRC_ROOT_PATH}
+        ${SRC_PATH}
+        ${TESTS_PATH}
+)
+
+# test.
+enable_testing()
+
+add_executable(
+        test_${PROBLEM_NAME}
+        ${TESTS_PATH}/test.cc
+)
+target_link_libraries(test_${PROBLEM_NAME} GTest::gtest_main)
+
+
+include(GoogleTest)
+gtest_discover_tests(test_${PROBLEM_NAME})

tests/5/test.cc

@@ -0,0 +1,8 @@
+#include <gtest/gtest.h>
+
+#include "utils/utils.h"
+#include "solution.hpp"
+
+TEST(longest_palindromic_substring_testing, BasicAssertions) {
+
+}

tests/CMakeLists.txt

@@ -10,3 +10,4 @@ add_subdirectory(63)
 add_subdirectory(120)
 add_subdirectory(931)
 add_subdirectory(221)
+add_subdirectory(5)