Cracking The Coding Interview 3.2

//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.

//使用一个链表来记录最小值的index 
#include <iostream>
using namespace std;
#define MAXSIZE 100
#define INIT -888888

class mStack
{
public:
	mStack()
	{
		top = -1;
		mi = new min;
		mi->data = 0;
		mi->nextMin = NULL;
		for (int i =0 ;i<100; i++)
		{
			data[i] = INIT;
		}
	}

	int pop()
	{
		if (top > -1)
		{
			if (top == mi->data)
			{
				min *t = mi;
				mi = mi->nextMin;
				delete t;
			}

			int c= data[top];
			data [top] = INIT;
			top --;
			return c;
		}
		else
			return -2;
	}

	bool push(int e)
	{
		if (top<MAXSIZE-1)
		{
			top++;
			data[top] = e;
			
			if (data[mi->data] > data[top] && data[top]!= INIT)
			{
				min *t = new min;
				t->data = top;
				t->nextMin = mi;
				mi = t;
			}
			return true;
		}
		else
		{
			return false;
		}
	}

	int getmin()
	{
		return data[mi->data];
	}

private:
	int data[MAXSIZE];
	int top;
	
	struct min
	{
		int data;
		min *nextMin;
	};
	min *mi;

};

int main()
{
	mStack s;
	
	for (int i=0;i<10;i++)
	{
		s.push(10-i);
	}

	s.pop();
	s.pop();
	cout<<s.getmin()<<endl;
	return 0;
}