Generate a unique value for a combination of two numbers

c# uniqueidentifier
NLV picture NLV · Nov 19, 2010 · Viewed 8.5k times · Source

Consider I've two numbers 1023232 & 44. I want to generate a unique number representing this combination of numbers. How can i generate it?

Requirement

f(x,y) = f(y,x) and f(x,y) is unique for every (x,y) or (y,x)

Answer

Botz3000 picture Botz3000 · Nov 19, 2010

if those are two ints, you could just do this:

ulong F(int x, int y) {
    ulong id = x > y ? (uint)y | ((ulong)x << 32) :  
                       (uint)x | ((ulong)y << 32);
    return id;
}

if you need to generate a truly unique value for two variables of a given size, you need about double the size of each variable. (ok, a bit less now that f(x,y) == f(y,x))

You could also get your original values back by reversing the same operation.

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