Data conversion

.gitignore

@@ -8,3 +8,5 @@ build/
 .idea/
 .vscode/
 *.swp
+
+cmake-*

README.md

@@ -93,7 +93,10 @@ handle it from there. :smile:
   * [Shunting yard](cpp/include/algorithm/string/shunting_yard.hpp) :white_check_mark:
   * Permutation
     * [Heap's Algorithm](cpp/include/algorithm/string/heaps_algorithm.hpp) :white_check_mark:
-
+* Utils
+  * [Data Conversion](cpp/include/utils/data_conversion.hpp)
+    * Convert to upper case :white_check_mark:
+    * Convert to lower case :white_check_mark:
 ### Data structures
 
 * Linked List

cpp/CMakeLists.txt

@@ -226,3 +226,10 @@ add_executable(fenwick_tree
         test/data_structure/tree/fenwick_tree.cpp)
 target_link_libraries(fenwick_tree test_runner)
 
+# ============================================================================
+# Utilities
+# ============================================================================
+
+add_executable(data_conversion
+               test/utils/data_conversion.cpp)
+target_link_libraries(data_conversion test_runner)

cpp/include/utils/data_conversion.hpp

@@ -0,0 +1,58 @@
+/*
+    Data Conversion
+    -------------------
+    Upper/Lower case algorithm using bit manipulation.
+
+    Time complexity
+    ---------------
+    O(N), where N is the length of the input.
+
+    Space complexity
+    ----------------
+    O(N), where N is the result.
+ */
+
+#ifndef DATA_CONVERSION_HPP
+#define DATA_CONVERSION_HPP
+
+#include <string>
+
+#define UPPER_CASE_BIT_MASK 0b11011111
+#define LOWER_CASE_BIT_MASK 0b00100000
+
+bool is_letter(char c) {
+    char lower_cased_char = (char)(c | LOWER_CASE_BIT_MASK);
+    return lower_cased_char >= 'a' && lower_cased_char <= 'z';
+}
+
+std::string make_upper_case(const std::string& input) {
+    std::string result;
+    for (auto c: input) {
+
+        if (is_letter(c)) {
+            result += c & UPPER_CASE_BIT_MASK;
+        }
+        else {
+            result += c;
+        }
+
+    }
+    return result;
+}
+
+std::string make_lower_case(const std::string& input) {
+    std::string result;
+    for (auto current_char: input) {
+
+        if (is_letter(current_char)) {
+            result += current_char | LOWER_CASE_BIT_MASK;
+        }
+        else {
+            result += current_char;
+        }
+
+    }
+    return result;
+}
+
+#endif //DATA_CONVERSION_HPP

cpp/test/utils/data_conversion.cpp

@@ -0,0 +1,31 @@
+#include "third_party/catch.hpp"
+#include "utils/data_conversion.hpp"
+
+#define NAME_SPACE "[utils][data-conversion][make_upper_case]"
+
+TEST_CASE("Base cases",  NAME_SPACE) {
+    REQUIRE(make_upper_case(" ") == " ");
+    REQUIRE(make_upper_case("1234567890") == "1234567890");
+    REQUIRE(make_upper_case("!@#$%^&*()_+±~<>.,|':;") == "!@#$%^&*()_+±~<>.,|':;");
+    REQUIRE(make_lower_case(" ") == " ");
+    REQUIRE(make_lower_case("1234567890") == "1234567890");
+    REQUIRE(make_lower_case("!@#$%^&*()_+±~<>.,|':;") == "!@#$%^&*()_+±~<>.,|':;");
+}
+
+TEST_CASE("Convert to upper case", NAME_SPACE) {
+    REQUIRE(make_upper_case("hello") == "HELLO");
+    REQUIRE(make_upper_case("world") == "WORLD");
+    REQUIRE(make_upper_case("GITHUB") == "GITHUB");
+    REQUIRE(make_upper_case("Cpp") == "CPP");
+    REQUIRE(make_upper_case("Hello World!") == "HELLO WORLD!");
+    REQUIRE(make_upper_case("Hello\nWorld!") == "HELLO\nWORLD!");
+}
+
+TEST_CASE("Convert to lower case", NAME_SPACE) {
+    REQUIRE(make_lower_case("HELLO") == "hello");
+    REQUIRE(make_lower_case("WORLD") == "world");
+    REQUIRE(make_lower_case("github") == "github");
+    REQUIRE(make_lower_case("Cpp") == "cpp");
+    REQUIRE(make_lower_case("Hello World!") == "hello world!");
+    REQUIRE(make_lower_case("Hello\nWorld!") == "hello\nworld!");
+}