For the first problem by pcyu

Makefile

all: p1 p2

p1: p1.cpp
	g++ -o p1 p1.cpp

p2: p2.cpp
	g++ -o p2 p2.cpp

clean:
	rm -f p1 p2

p1.cpp

#include <iostream>
#include <algorithm>
#include <iterator>

using namespace std;

bool reverse_int(int a, int b){
	return a>b;
}

class XXX{
private:
    int *array;
    int size;
public:
    XXX(int n){
        size = n;
        array = new int[n];
		for(int i=0;i<n;i++)
			array[i] = i;
	}
    ~XXX(){
        free(array);
    }
    void sorting(){
        // 這邊要怎麼用 qsort / STL algorithm sort 來寫
		sort(array, array+size, reverse_int);
    }
	void print(){
		copy(array, array+size, ostream_iterator<int>(cout, " "));
		cout << endl;
	}
};

int main(int argc, const char *argv[])
{
	XXX xxx(10);

	xxx.print();
	xxx.sorting();
	xxx.print();
	return 0;
}

p2.cpp

#include <iostream>
#include <algorithm>
#include <iterator>

using namespace std;

class Comparer{
	int *target;
public:
	Comparer(int *d){this->target = d;}
	bool operator()(int a, int b){
		return target[a] > target[b];
	}
};

class A{
private:
	int *data;
    int *index;
    int size;
public:
    A(int n){
        size = n;
        data = new int[n];
        index = new int[n];
		for(int i=0;i<n;i++){
			data[i] = i;
			index[i] = i;
		}
	}
    ~A(){
        free(data);
        free(index);
    }
    void sorting(){
		sort(index, index+size, Comparer(data));
    }
	void print(){
		cout << "data: ";
		copy(data, data+size, ostream_iterator<int>(cout, " "));
		cout << endl;
		cout << "index: ";
		copy(index, index+size, ostream_iterator<int>(cout, " "));
		cout << endl;
	}
};

int main(int argc, const char *argv[])
{
	A a(10);

	a.print();
	a.sorting();
	a.print();
	return 0;
}