Question

I have the following C formula

bucket = (hash - _min) * ((_capacity-1) / range());

What I need to to rearrange the equation to return the _capacity instead of bucket (I have all other variables apart from _capacity). e.g.

96 = (926234929-805306368) * (( x -1) /1249540730)
836 = (1852139639-805306368) * ((x -1) /1249540730)

As you can see it’s a fairly simple equation, all I need is x on the left. But my algebra is very rusty, so any help appreciated.

Answer 1

capacity = (range() * bucket) / (hash - _min) + 1;

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bucket = (hash - _min) * ((_capacity - 1) / range()); // start
bucket = ((hash - _min) * (_capacity - 1)) / range(); // rearrange
range() * bucket = (hash - _min) * (_capacity - 1); // multiply by range
(range() * bucket) / (hash - _min) = _capacity - 1; // divide by (hash - _min)
(range() * bucket) / (hash - _min) + 1 = _capacity; // add 1
capacity = (range() * bucket) / (hash - _min) + 1; // rearrange