For some people, learning the OLL step of the Fridrich Method can be difficult. By learning a few shortcuts, there won't be any need to learn all 57 algorithms.
You can use just one algorithm: F R U R' U' F'.
This algorithm can take most OLL cases and solve them.
But do note that that means you will be slower then learning all algorithms.
The Sequence[]
By just knowing the F R U R' U' F' algorithm, you can get these cases solved.
In first case or fourth case if you do F R U Ri Ui, you can get cross.