# help with number calculation algorithm [hw]

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Published on 2010-03-06T11:58:46Z
Indexed on
2010/05/15
20:24 UTC

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Hi -

I'm working on a hw problem that asks me this:

given a finite set of numbers, and a target number, find if the set can be used to calculate the target number using basic math operations (add, sub, mult, div) and using each number in the set **exactly** once (so I need to exhaust the set). This has to be done with recursion.

So, for example, if I have the set

```
{1, 2, 3, 4}
```

and target 10, then I could get to it by using

```
((3 * 4) - 2)/1 = 10.
```

I'm trying to phrase the algorithm in pseudo-code, but so far haven't gotten too far. I'm thinking graphs are the way to go, but would definitely appreciate help on this. thanks.

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