这个最简单了，就是用一个最大值栈和一个最小值栈来维护最值信息。

template
      

class stack_ext : public stack
      

{

public:

void push(const typename stack
      
       ::value_type &t)
      

{

if (m_sMax.empty() || t >= m_sMax.top())

{

m_sMax.push(t);

}

if (m_sMin.empty() || t <= m_sMin.top())

{

m_sMin.push(t);

}

stack
      
       ::push(t);
      

}

void pop()

{

if (!m_sMax.empty() && stack
      
       ::top() == m_sMax.top())
      

{

m_sMax.pop();

}

if (!m_sMin.empty() && stack
      
       ::top() == m_sMin.top())
      

{

m_sMin.pop();

}

stack
      
       ::pop();
      

}

typename stack
      
       ::const_reference max_val() const
      

{

return m_sMax.top();

}

typename stack
      
       ::const_reference min_val() const
      

{

return m_sMin.top();

}

private:

stack
      
        m_sMin;
      

stack
      
        m_sMax;
      

};