diff --git a/case_study/readme.md b/case_study/readme.md
new file mode 100644
index 0000000..e69de29
diff --git a/case_study/use_array.cpp b/case_study/use_array.cpp
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--- /dev/null
+++ b/case_study/use_array.cpp
@@ -0,0 +1,133 @@
+#include <iostream>
+#include <string>
+#include <stdexcept>
+class Stack{
+    private://abstraksi dynamic array
+        int size;
+        int capacity;
+        char* arr;
+    private:
+        std::string s;
+    public:
+        //default constructor
+        Stack()noexcept{
+            this->capacity = 1;
+            this->size = 0;
+            this->s = "";
+            this->arr = new char[capacity];
+        }
+        //constructor
+        Stack(int capacity,std::string s){
+            this->capacity = capacity;
+            this->size = 0;
+            this->s = s;
+            this->arr = new char[capacity];
+        }
+    private: //method valid parantheses
+        bool is_open(char bracket){
+            if(bracket == '{'){
+                return true;
+            }
+            if(bracket == '('){
+                return true;
+            }
+            if(bracket == '['){
+                return true;
+            }
+            return false;
+        }
+        bool is_close(char bracket){
+            if(bracket == '}'){
+                return true;
+            }
+            if(bracket == ')'){
+                return true;
+            }
+            if(bracket == ']'){
+                return true;
+            }
+            return false;  
+        }
+        bool is_matching(char open,char close){
+            if(open == '{' && close == '}'){
+                return true;
+            }
+            if(open == '(' && close == ')'){
+                return true;
+            }
+            if(open == '[' && close == ']'){
+                return true;
+            }
+            return false;
+        }
+        std::string parser(){
+            std::string res;
+            for(int i = 0;i < this->s.size();i++){
+                if(isalnum(s[i])){
+                    res.push_back(s[i]);
+                }
+            }
+            return res;
+        }
+    private://getter stack
+        char top()const noexcept{
+            return arr[size - 1];
+        }
+        bool is_empty()const noexcept{
+            if(size == 0){
+                return true;
+            }
+            return false;
+        }
+    private:
+        void push(const char& bracket)noexcept{
+            arr[size] = bracket;
+            size++;
+        }
+        void pop(){
+            if(size == 0){
+                throw std::runtime_error("Stack kosong");
+            }
+            arr[size - 1] = 0;
+            size--;
+        }
+    public: 
+        bool valid_parantheses(){
+            std::string res = parser();
+            for(int i = 0;i < res.size();i++){
+                if(is_open(res[i])){
+                    //push ke stack
+                    arr[size] = res[i];
+                    size++;
+                }else if(is_close(res[i])){
+                    //jika kosong maka tidak ada pasangan
+                    if(is_empty()){
+                        return false;
+                    }
+                    //jika tidak matching langsung return false
+                    if(!is_matching(arr[size - 1],res[i])){
+                        return false;
+                    }
+                    //pop jika matching
+                    arr[size - 1] = 0;
+                    size--;
+                }
+            }
+            return true;
+        }
+    void result(){
+        if(valid_parantheses()){
+            std::cout << "Bracket valid" << std::endl;
+        }else{
+            std::cout << "Bracket tidak valid" << std::endl;
+        }
+
+    }        
+};  
+int main(){
+    Stack* stack1 = new Stack(100,"(a+b)");
+    stack1->result();
+    // Your code here
+    std::cin.get();
+    return 0;
+}
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