How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push, pop and min should all operate in O(1) time.

1 template
     
       2 class StackWithMin 3 { 4 public: 5     stack() 6     { 7         stackTop = -1; 8         minStackItemIndex = -1; 9     }10     void Push(T x)11     {    stackTop++;12         if(stackTop>MAXN)13            //超出栈的最大存储量；14         else 15         {16             stackItem[stackTop] = x;17             if(x
      
       =0)44             return stackItem[minStackItemIndex];45         else46             return INT_MAX;47     }48     49 private:50     T stackItem[MAXN];51     int stackTop;52     int NextMinItem[MAXN];53     int minStackItemIndex;54 55 };