static VALUE
rb_ary_uniq(VALUE ary)
{
    VALUE hash,uniq,v;
    long i;

    if (RARRAY_LEN(ary) <= 1)
        return rb_ary_dup(ary);
    if (rb_block_given_p()) {
        hash = ary_make_hash_by(ary);
        uniq = ary_new(rb_obj_class(ary),RHASH_SIZE(hash));
        st_foreach(RHASH_TBL(hash),push_value,uniq);
    }
    else {
        hash = ary_make_hash(ary);
        uniq = ary_new(rb_obj_class(ary),RHASH_SIZE(hash));
        for (i=0; i<RARRAY_LEN(ary); i++) {
            st_data_t vv = (st_data_t)(v = rb_ary_elt(ary,i));
            if (st_delete(RHASH_TBL(hash),&vv,0)) {
                rb_ary_push(uniq,v);
            }
        }
    }
    ary_recycle_hash(hash);

    return uniq;

它具有O(N)复杂性