Creating Set of sequnces(12345678)
<p>I would like to create set of strings and below is the only limitation.
Same digit should not repeat.</p>

<p>string Range 1-8(12345678) or 1-16(12345678910111213141516)<br>
For example:(set of series)</p>

<pre><code>12345678
12345687
12345876
12345867
...
...
87654321
</code></pre>

<p>Like that 2^8(1-8) and 2^16(1-16) possibilities are there.
How can i generate these strings very efficiently with less computation?</p>
