Efficient way of finding distance between two 3D points

Question

I am writing a code in C++ and want to compute distance between two points. Question 1:

I have two points P(x1, y1, z1) and Q(x2, y2, z2) , where x,

Answer 1

Note that when using sqrt(dx*dx+dy*dy+dz*dz) the sum of squares might overflow. hypot(dx, dy) computes a distance directly without any chance of overflow. I'm not sure of the speediest 3d equivalent, but hypot(dx, hypot(dy, dz)) does the job and won't overflow either.