Quick Sort

qsort.cpp

#include <iostream>
#include "qsort.hpp"
using std::cin;
using std::cout;


const int maxn = 100;


struct Vector {
	int x;
	int y;
	bool operator< (const Vector &p2){
		Vector &p1 = *this;
		return ((p1.x*p1.x+p1.y*p1.y) < (p2.x*p2.x+p2.y*p2.y));
	}
	friend std::ostream& operator<< (std::ostream &left, const Vector &right){
		left << "(" << right.x << ", " << right.y << ")";
	}
};


bool compare(const Vector &p1, const Vector &p2){
	return (p1.y < p2.y);
}


int main(int argc, char *argv[]){
	Vector data[maxn];

	int i = 0;
	while(!cin.eof() && i < maxn && cin >> data[i].x >> data[i].y){
		i++;
	}
	int count = i;

	qsort(data, data+count-1, compare);
	
	for(i=0; i<count; i++){
		cout << data[i];
	}
	cout << '\n';

	qsort(data, data+count-1);
	
	for(i=0; i<count; i++){
		cout << data[i];
	}
	cout << '\n';

	return 0;
}

qsort.hpp

template <class Type>
void qsort(Type *head, Type *tail, bool (*compare)(const Type &, const Type &) = NULL){
	//std::cout << "sort:" << *head << " " << *tail << '\n';
	Type *middle = (head + (tail-head)/2);
	Type *left = head;
	Type *right = head;
	Type pivot = *middle;

	Type temp = *tail;
	*tail = pivot;
	*middle = temp;

	while(left < tail){
		if(compare? compare(*left, pivot): *left < pivot){
			temp = *right;
			*right = *left;
			*left = temp;
			right++;
		}
		left++;
	}

	temp = *tail;
	*tail = *right;
	*right = temp;

	if(right+1 < tail)
		qsort(right+1, tail, compare);
	if(head < right-1)
		qsort(head, right-1, compare);
}