code: func uniqueMergeSortedStrings(ls, rs []string) []string {
  	varSet := make([]string, len(ls)+len(rs))
  	for i := 0; ; i++ {
  		if len(ls) == 0 {
  			rs, ls = ls, rs
  		}
  		if len(rs) == 0 {
  			i += copy(varSet[i:], ls)
  			return varSet[:i]
  		}
  		assert(i < len(varSet))
  		assert(len(rs) > 0 && len(ls) > 0)
  		if ls[0] > rs[0] {
  			ls, rs = rs, ls
  		}
  		if ls[0] < rs[0] {
  			varSet[i] = ls[0]
  			ls = ls[1:]
  		} else {
  			varSet[i] = ls[0]
  			ls, rs = ls[1:], rs[1:]
  		}
  	}
  }
docs: // uniqueMergeSortedStrings merges two sorted sets of string (as slices) and removes duplicates.