Added Decode String

CMakeLists.txt

@@ -1206,4 +1206,15 @@ add_executable(AsteroidCollision
 target_link_libraries(
         AsteroidCollision
         GTest::gtest_main
+)
+
+# Decode String
+add_executable(DecodeString
+        Medium/DecodeString/include/solution.hpp
+        Medium/DecodeString/tests/test.cpp
+)
+
+target_link_libraries(
+        DecodeString
+        GTest::gtest_main
 )

Medium/DecodeString/include/solution.hpp

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stack>
+#include <vector>
+#include <iostream>
+#include <algorithm>
+#include <gtest/gtest.h>
+
+class Solution {
+public:
+    static auto decode_string(const std::string &word) -> std::string {
+        std::stack<std::string> substrings;
+        std::stack<size_t> multipliers;
+        size_t multiplier = 0;
+        std::string current_sub;
+
+        for (const char &ch : word) {
+            if (isdigit(ch)) {
+                multiplier = multiplier * 10 + (ch - '0');
+            } else if (ch == '[') {
+                multipliers.push(multiplier);
+                substrings.push(current_sub);
+                multiplier = 0;
+                current_sub.clear();
+            } else if (ch == ']') {
+                size_t repeat_count = multipliers.top();
+                multipliers.pop();
+                std::string previous_sub = substrings.top();
+                substrings.pop();
+                for (size_t i = 0; i < repeat_count; ++i) {
+                    previous_sub += current_sub;
+                }
+                current_sub = previous_sub;
+            } else current_sub += ch;
+        }
+
+        return current_sub;
+    }
+};

Medium/DecodeString/tests/test.cpp

@@ -0,0 +1,38 @@
+#include "../include/solution.hpp"
+
+class DecodeString : public ::testing::Test {
+protected:
+    ~DecodeString() override = default;
+};
+
+TEST_F(DecodeString, FirstTest) {
+    std::string word = "3[a]2[bc]";
+
+    std::string result = Solution::decode_string(word);
+
+    std::string expected = "aaabcbc";
+    ASSERT_EQ(result, expected);
+}
+
+TEST_F(DecodeString, SecondTest) {
+    std::string word = "3[a2[c]]";
+
+    std::string result = Solution::decode_string(word);
+
+    std::string expected = "accaccacc";
+    ASSERT_EQ(result, expected);
+}
+
+TEST_F(DecodeString, ThirdTest) {
+    std::string word = "2[abc]3[cd]ef";
+
+    std::string result = Solution::decode_string(word);
+
+    std::string expected = "abcabccdcdcdef";
+    ASSERT_EQ(result, expected);
+}
+
+auto main(int argc, char **argv) -> int {
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}