More on KSubsets

• To: mathgroup at smc.vnet.net
• Subject: [mg2429] More on KSubsets
• From: wself at viking.emcmt.edu (Will Self)
• Date: Wed, 8 Nov 1995 23:41:42 -0500

```Axel's question about KSubsets has some interesting variations.
For example, there is another possibly useful order on the k-subsets,
different from the lexicographic one.  For a finite subset s of the non-negative integers, compute the number n such that the digits in the
binary representation for n corresponding to elements of s are 1, and the
rest of the digits are 0.  For the set {0,1,3} the associated number would
be 2^0 + 2^1 + 2^3 = 11.

Now you can order the subsets s according to their associated numbers n.
It's no problem to create the function nthSubset, which gives the nth
subset in this ordering, but what about the function nthKSubset, which
for a given k would return the nth k-subset in this ordering?  Anyone
have a nice way to do this?

Will Self

```

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