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copied!<p>I think this is close to what you ask: A constant, reasonably even distribution of the items in an array. </p> <pre><code>// The input array. 0s are regarded as blanks. $array = array(1,1,1,1,2,2,2,2,3,3,3,3,3,3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0); // Count the times each item occurs. PHP will probably have a function for that, but I don't know. $counter = array(); foreach ($array as $item) { // Zeros are infill. Don't process them now, only process the other numbers and // the zeros will occupy the remaining space. if ($item === 0) continue; if (!array_key_exists($item, $counter)) $counter[$item] = 0; $counter[$item]++; } // Reverse sort by quantity. This results in the best distribution. arsort($counter); // Pre-fill a new array with zeros. $resultCount = count($array); $result = array_fill(0, $resultCount, 0); // Distribute the items in the array, depending on the number of times they occur. foreach ($counter as $item => $count) { // Determine the division for this item, based on its count. $step = $resultCount / $count; // Add the item the right number of times. for ($i = 0; $i < $count; $i++) { // Start with the index closest to the preferred one (based on the calculated step). $index = 0; $startIndex = (int)($step * $i); // Count up until a right index is found. for ($index = $startIndex; $index < $resultCount; $index++) { if ($result[$index] === 0) { $result[$index] = $item; break; } } // If no proper index was found, count fown from the starting index. if ($index === $resultCount) { for ($index = $startIndex; $index >= 0; $index--) { if ($result[$index] === 0) { $result[$index] = $item; break; } } } // Still no proper index found, that shouldn't be possible. There's always room. if ($index === -1) { throw new Exception('This cannot not happen'); } } } var_dump($result); </code></pre> <p>For array:</p> <pre><code>1,1,1,1,2,2,2,2,3,3,3,3,3,3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 </code></pre> <p>It returns:</p> <pre><code>3,2,1,0,3,0,0,0,3,0,2,1,3,0,0,0,3,0,0,0,0,3,2,1,0,3,0,0,0,3,0,2,1,3,0,0,0,3,0,0,0,0 </code></pre> <p>For array:</p> <pre><code>1,1,1,1,2,2,2,2,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,0,0 </code></pre> <p>It returns:</p> <pre><code>4,4,3,4,3,4,2,4,3,4,2,4,3,4,1,4,3,4,1,4,0,4,4,3,4,3,4,2,4,3,4,2,4,3,4,1,4,3,4,1,4,0 </code></pre> <p>Which I think is a neat distribution. Thanks to datdo for the idea of sorting the intermediate array.</p>

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