Weight training is an excellent way of building strength but for combat sports like UFC I think
bodyweight exercises have an edge because the constant practise of using your own
bodyweight as the form of resistance means that you become far more effective at
moving your own body through space with speed and
explosive power which after all is essential in mma.
There are several good
bodyweight leg exercises that are perfect for the job but remember that to build
explosive power you need to choose exercises that are demanding and allow you to
move your legs with speed as strength x speed = power