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    <p>Firstly, I will make a big assumption that "better" means "I do not want any/as few new data structures".</p> <p>If this is the case, then the simplest solution is the best, since I don't need to bother optimising by time. I know that the other solutions are much more elegant, I've only posted it because I've read the question as "make sure it's minimal space-wise".</p> <pre><code>private static String rotate( final char[] a, final int n ) { for(int i = 0; i &lt; n; i++) { char tmp = a[a.length-1]; for(int j = a.length-1; j &gt;= 0; j--) { a[j] = j == 0 ? tmp : a[(j-1+a.length)%a.length]; } } return new String(a); } </code></pre> <p>So I hacked this out pretty quickly. Basically, I'm just doing rotates by lengths of one until I've rotated <code>n</code> number of times. To optimise it you probably could take <code>gcd(n, a.length)</code>.</p> <p>Now, since my solution is pretty terrible, I'll also post the following code taken from <a href="http://www.leetcode.com/2010/04/rotating-array-in-place.html" rel="noreferrer">here</a></p> <pre><code>void reverse_string(char* str, int left, int right) { char* p1 = str + left; char* p2 = str + right; while (p1 &lt; p2) { char temp = *p1; *p1 = *p2; *p2 = temp; p1++; p2--; } } void rotate(char* str, int k) { int n = strlen(str); reverse_string(str, 0, n-1); reverse_string(str, 0, k-1); reverse_string(str, k, n-1); } </code></pre> <p>This is, what I assume to be a C-style implementation that runs faster than mine, using a basic idea that with three reverses, you can implement an inline shift.</p> <p>As is said here,</p> <blockquote> <p>The trick is to do three reverse operation. One for the entire string, one from index 0 to k-1, and lastly index k to n-1. Magically, this will yield the correct rotated array, without any extra space! (Of course, you need a temporary variable for swapping).</p> </blockquote> <p>I haven't verified this property on the blog I've linked to, so I will post it with a grain of salt that it would appear to work but I've never tested it myself...</p>
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    1. COyou actually do not need any tmp variable for swapping if you think about it! ;)
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    2. COIn C or C++ you should rotate by memory movement. But the question was on java...
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    3. CO@Gevorg, I'm sure you're right, XOR swaps and other things that I'm bad at remembering vaguely come to mind =P There are much cooler and more efficient ways for swapping things that I don't remember at all ^^'
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