feat: add quiz 2 counter.

CMakeLists.txt

@@ -6,3 +6,4 @@ set(CMAKE_CXX_STANDARD 11)
 add_subdirectory(third-party/googletest-1.17.0)
 
 add_subdirectory(mixplus)
+add_subdirectory(counter)

counter/CMakeLists.txt

@@ -0,0 +1,11 @@
+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
+
+aux_source_directory(${CMAKE_CURRENT_SOURCE_DIR}/src SRC)
+
+add_library(libcount STATIC ${SRC})
+
+add_executable(counter main.cpp)
+
+target_link_libraries(counter libcount)
+
+add_subdirectory(tests)

counter/include/counter.h

@@ -0,0 +1,15 @@
+#include <string>
+#include <unordered_map>
+
+namespace counter
+{
+    struct Counter
+    {
+        static std::unordered_map<std::string, long> count(const std::string& input);
+
+        static void countPair(std::unordered_map<std::string, long>& map, const std::string& input);
+
+
+        static void countTriple(std::unordered_map<std::string, long>& map, const std::string& input);
+    };
+}

counter/main.cpp

@@ -0,0 +1,21 @@
+#include <counter.h>
+#include <iostream>
+
+int main(const int argc, char** argv)
+{
+    if (argc != 2)
+    {
+        std::cout << "ERROR: Need a string." << std::endl;
+    }
+
+    const std::string input(argv[1]);
+
+    const auto map = counter::Counter::count(input);
+
+    for (const auto& pair : map)
+    {
+        std::cout << pair.first << ' ' << pair.second << std::endl;
+    }
+
+    return 0;
+}

counter/src/counter.cpp

@@ -0,0 +1,34 @@
+#include "counter.h"
+
+
+void counter::Counter::countPair(std::unordered_map<std::string, long>& map, const std::string& input)
+{
+    for (int i = 1; i < input.size(); i++)
+    {
+        const auto pair = input.substr(i - 1, 2);
+
+        map[pair] += 1;
+    }
+}
+
+void counter::Counter::countTriple(std::unordered_map<std::string, long>& map, const std::string& input)
+{
+    for (int i = 2; i < input.size(); i++)
+    {
+        const auto pair = input.substr(i - 2, 3);
+
+        map[pair] += 1;
+    }
+}
+
+std::unordered_map<std::string, long> counter::Counter::count(const std::string& input)
+{
+    std::unordered_map<std::string, long> map;
+
+    countPair(map, input);
+    countTriple(map, input);
+
+    return map;
+}
+
+

counter/tests/CMakeLists.txt

@@ -0,0 +1,10 @@
+enable_testing()
+
+aux_source_directory(${CMAKE_CURRENT_SOURCE_DIR} TEST_SRC)
+
+add_executable(
+        counter_tests
+        ${TEST_SRC}
+)
+
+target_link_libraries(counter_tests GTest::gtest_main libcount)