python math domain errors in math.log function

As long as your input is within the half-open interval (0, 1] (not including 0), you are fine. You can’t be too close to zero: So simply checking for exactly zero (maybe as the result of an underflow) should be enough, or alternatively catch the exception and handle it. EDIT: This also holds for the … Read more

Probability of hash collision

Let’s imagine we have a truly random hash function that hashes from strings to n-bit numbers. This means that there are 2n possible hash codes, and each string’s hash code is chosen uniformly at random from all of those possibilities. The birthday paradox specifically says that once you’ve seen roughly √(2k) items, there’s a 50% chance … Read more

How to save decimal in java

Initialize your variable with an expression that evaluates to a double rather than an int: Otherwise the expression is done using integer arithmetic (which ends up truncating the result). That truncated result then gets converted to a double.

Mapping a numeric range onto another

Let’s forget the math and try to solve this intuitively. First, if we want to map input numbers in the range [0, x] to output range [0, y], we just need to scale by an appropriate amount. 0 goes to 0, x goes to y, and a number t will go to (y/x)*t. So, let’s reduce your problem to the above simpler problem. … Read more

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