1. define a class of rectangle:

class rectangle()

{    

    private: int w,h;

    void setparameter(int w_, int h_)

    {w=w_;h=h_;}

    int area()

    { return w*h;}

    int perimeter()

    { return 2*(w+h);}

};

void main()

{    int w,h;

    rectangle c;

    cin>>w>>h;

    c.setparameter(w,h);

    cout<<c.area()<<endl<<c.perimeter()<<endl;

    return 0;

}

2. count matched brackets in a string:

#include <iostream>

#include <stack>

using namespace std;

int countbrackets(string s)

{    

    if (s.size()==0)    return 0;

    int n=0;

    stack <char> cstack;

    for (char c:s)

    {    if (c=="(")    

            {cstack.push(c);}

          else if(c==")")

            {if (c==cstack.top())

                {    cstack.pop();

                    n++;

                }

            }

    }

    return n;

}