Input: careermonk
Output: camonk

Input: mississippi
Output: m

I want to improve this code.

#include <iostream> #include <string>  #define max 1000  class Stack {   int top; public:   char stk[max];   Stack()   {     top = -1;   }   bool isStackEmpty();   void push(char);   char pop();   std::string modifyString(std::string); private:   void removeAdjacentDuplicate(std::string); };  bool Stack::isStackEmpty() {    if (top == -1)       return true;    else       return false; }  void Stack::push(char val) {    int s = max - 1;    if (top < s)    {      top = top + 1;      stk[top] = val;    }    else     std::cerr << "Stack Overflow \n"; }  char Stack::pop() {    if (isStackEmpty() == true)        std::cerr << "Stack Underflow \n";    else    {       --top;       return stk[top + 1];    } }  void Stack::removeAdjacentDuplicate(std::string str) {    int len = str.length();    for (int i = 0; i < len; i++)    {       if (isStackEmpty() == true)       {          push(str[i]);       }       else if (str[i] == stk[top])       {          int discard = pop();       }       else       {          push(str[i]);       }    } }  std::string Stack::modifyString(std::string str) {    removeAdjacentDuplicate(str);    str.resize(top + 1);    for (int i = 0; i <= top; i++)    {      str[i] = stk[i];    }    str[top + 1] = '';    return str; }  int main() {    Stack stack1;    std::string str = "careermonk";    std::cout << "Orignal string : " << str << "\n";    str = stack1.modifyString(str);    std::cout << "New string     : " << str << "\n";     Stack stack2;    std::string str2 = "mississippi";    std::cout << "Original string : " << str2 << "\n";    str2 = stack2.modifyString(str2);    std::cout << "New string      : " << str2 << "\n"; }