Some people might also suggest another method for the problem but I would rather request everybody to just tell me about how to solve the above issue as more than just solving the problem , I want to learn one new method which will be more beneficial . :)

Your comparison operation is not symmetric.

Here is your code:

    bool operator()(const Point& a,const Point& b)
    {
        if(a.getfirst()>b.getfirst())
        {
            return true;
        }
        else
        {
            if(a.getsecond()>b.getsecond())
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

See, if a.x > b.x, you return true. Then, by symmetry, if a.x < b.x, the function should return false. But it compares the y part instead.

You can insert the missing a.x < b.x case and check if it's any better, like this:

    bool operator()(const Point& a,const Point& b)
    {
        if(a.getfirst()>b.getfirst())
        {
            return true;
        }
        else if(a.getfirst()<b.getfirst())
        {
            return false;
        }
        else
        {
            if(a.getsecond()>b.getsecond())
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

On a side note, does a.getfirst(), a.getsecond() make much sense here? The whole "private individual coordinates with obscurely named getters and setters" looks like overengineering to me. Perhaps naming the fields x and y and accessing them directly would be more, well, to the point.

And on another side note, your template's #define ipow(a,b) (int)pow(a,b) is dangerous. Half of possible compilers will give you 5² = 24 with it. You might want to add something (for example, 0.5), and only then convert to an integer.