Use Reservoir sampling when 1 element (equal priorities) has to be picked

[ndsvw]

https://en.wikipedia.org/wiki/Reservoir_sampling#Optimal:_Algorithm_L

https://www.geeksforgeeks.org/select-a-random-number-from-stream-with-o1-space/?ref=lbp
https://www.geeksforgeeks.org/reservoir-sampling/