技巧：快速写表达式：

include [HTML_REMOVED]

include [HTML_REMOVED]

int main()
{
double x1, y1, x2, y2;
scanf(“%lf%lf”, &x1, &y1);
scanf(“%lf%lf”, &x2, &y2);
printf(“%.4lf\n”, sqrt((x1 - x2) * (x1 -x2) + (y1 - y2) * (y1 - y2)));

return 0;

}