shithub: kwa

ref: d38caa1bee4fc59e86f2cc1de2787d319ac2bffe
dir: /test/t.randk/

{
	k = 2
	n = NF
	i = 1
	while ( i <= n ) {
		if ( rand() < k/n ) {
			print i
			k--
		}
		n--
		i++
	}
}