[C++] 두 점 사이의 거리 구하기

#include <iostream>
#include <cmath>

using namespace std;
double length(double x1, double y1, double x2, double y2);

int main(void)
{
	double X1=0, Y1=0;
	double X2=0, Y2=0; 
	
	cin >> X1;
	cin >> Y1;
	cin >> X2;
	cin >> Y2;
	cout << "(" << X1 << "," << Y1 << ")와 (" << X2 << "," << Y2 << ") 사이의 거리는?\n";
	cout << "Distance : " << sqrt(length(X1, Y1, X2, Y2));
	return 0;
}

double length(double x1, double y1, double x2, double y2)
{
	double distance = ((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
	return distance;
}