Determining Number of Iterations in a loop (Java)

The formula stated in this question works for for loops where i is being added to or subtracted from. My question is how can this formula be changed to give the number of iterations in a for loop where i is being divided or multiplied by a value.

@WJS

CodePudding user response：

for(int i = M; i < N; i*=k) 
  ...

The critical point is when we have been through this loop s times, so that i = M k^s = N. Take the logarithm of both sides:

log(M)   s log(k) = log(N)

s = (log(N)-log(M))/log(k)

Use the floor function for <= and the ceiling function (minus one) for < (which is what WJS did in the linked question). I don't know Java, so I won't attempt to write Java code.

(There might be a problem if you are multiplying an integer counter by a floating-point factor, or something like that, but I will not accept responsibility for such foolishness.)