how to change stack value c++ code example

Example: get last element of stack c++

// stack::top
#include <iostream>       // std::cout
#include <stack>          // std::stack

int main ()
{
  std::stack<int> mystack;

  mystack.push(10);
  mystack.push(20);
  // .top() gets the last/top element of stack c++
  mystack.top() -= 5;

  std::cout << "mystack.top() is now " << mystack.top() << '\n';

  return 0;
}