1 class MinStack { 2 public: 3     MinStack() { 4         // do initialization if necessary 5     } 6  7     void push(int number) { 8         // write your code here 9         if (minimum.empty() || number <= minimum.top())10             minimum.push(number);11         data.push(number);12     }13 14     int pop() {15         // write your code here16         if (minimum.top() == data.top())17             minimum.pop();18         int elem = data.top();19         data.pop();20         return elem;21     }22 23     int min() {24         // write your code here25         return minimum.top();26     }27 private:28     stack
     
       data;29     stack
      
        minimum;30 };