Get minimum element from stack

PROBLEM :
Implement a Stack in which you can get min element in O(1) time and O(1) space.

Input (To be used for Expected Output):
The first line of the input contains an integer 'T' denoting the number of test cases. Then T test cases follow.
First line of each test case contains an integer Q denoting the number of queries .
A Query Q is of 3 Types
(i)   1 x (a query of this type means  pushing 'x' into the stack)
(ii)  2 (a query of this type means to pop element from stack and print the poped element)
(iii) 3 (a query of this type means to print the minimum element from the stack)

The second line of each test case contains Q queries seperated by space.

Output:

The output for each test case will  be space separated integers having -1 if the stack is empty else the element poped out  or min element from the stack .
You are required to complete the three methods push which take one argument an integer 'x' to be pushed into the stack , pop which returns a integer poped out from the stack and getMin which returns the min element from the stack.

Constraints:
1<=T<=100
1<=Q<=100
1<=x<=100

Example:
Input
1
6
1 2 1 3 2 3 1 1 3  

Output
3 2 1

Explanation:
In the first test case for query
1 2    the stack will be {2}
1 3    the stack will be {2 3}
2       poped element will be 3 the stack will be {2}
3       min element will be 2
1 1    the stack will be {2 1}
3       min element will be 1 and

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SIMPLE c++ IMPLEMENTATION :
--------------------------------------------------------------------------------

/*
The structure of the class is as follows
class _stack{
stack<int> s;
int minEle;
public :
    int getMin();
    int pop();
    void push(int);
};
*/

/*returns min element from stack*/
int _stack :: getMin()
{
    if(s.empty())
        return -1 ;
    return minEle ;
}

/*returns poped element from stack*/
int _stack ::pop()
{
    if(s.empty())
        return -1 ;
     
    if(s.top()<minEle)
    {
        int ele=s.top() ;
        s.pop() ;
        int k=minEle ;
        minEle=minEle-ele ;
        return (k) ;
    }
    else
    {
        int ele=s.top() ;
        s.pop() ;
        return ele ;
    }
}

/*push element x into the stack*/
void _stack::push(int x)
{
    if(s.empty())
    {
        s.push(x) ;
        minEle=x ;
        return ;
    }
 
    if(x<minEle)
    {
        s.push(x-minEle) ;
        minEle=x ;
    }
    else
        s.push(x) ;
}


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