function mergeSort($list)
{
$length = count($list);
$res = [];
if ($length > 1) {
$chunks = array_chunk($list, ceil($length / 2));
$firstChunk = mergeSort($chunks[0]);
$secondChunk = mergeSort($chunks[1]);
$i = 0;
$j = 0;
while ($i < count($firstChunk)) {
if ($firstChunk[$i] > $secondChunk[$j]) {
$res[] = $secondChunk[$j];
$j++;
} else {
if ($firstChunk[$i] < $secondChunk[$j]) {
$res[] = $firstChunk[$i];
$i++;
}
}
if (!array_key_exists($i, $firstChunk)) {
$res = array_merge($res, array_slice($secondChunk, $j, count($secondChunk)));
break;
}
if (!array_key_exists($j, $secondChunk)) {
$res = array_merge($res, array_slice($firstChunk, $i, count($firstChunk)));
break;
}
}
} else {
return $list;
}
return $res;
}
function mergeSort(array &$a, $first, $last, $temp)
{
if ($first < $last) {
$mid = (int) (($first + $last) / 2);
mergeSort($a, $first, $mid, $temp);
mergeSort($a, $mid + 1, $last, $temp);
mergeArray($a, $first, $mid, $last, $temp);
}
}
function mergeSort($array)
{
if (count($array) < 2) {
return $array;
}
$mid = count($array) / 2;
echo "<h5>Splitting " . json_encode($array) . " ===> Left: " . json_encode(array_slice($array, 0, $mid)) . " Right: " . json_encode(array_slice($array, $mid));
$right = mergeSort(array_slice($array, 0, $mid));
$left = mergeSort(array_slice($array, $mid));
return merge($left, $right);
}
function mergeSort(array $arr)
{
$count = count($arr);
if ($count <= 1) {
return $arr;
}
$left = array_slice($arr, 0, (int) ($count / 2));
$right = array_slice($arr, (int) ($count / 2));
$left = mergeSort($left);
$right = mergeSort($right);
return merge($left, $right);
}
function mergeSort($array)
{
if (count($array) < 2) {
return $array;
}
if (count($array) < 3) {
echo "<h5>Splitting " . json_encode($array) . " ===>" . " Part #1: " . json_encode(array($array[0])) . " Part #2: " . json_encode(array($array[1]));
return merge(array($array[0]), array($array[1]));
}
$part = (int) (count($array) / 3);
echo "<h5>Splitting " . json_encode($array) . " ===>" . " Part #1: " . json_encode(array_slice($array, 0, $part)) . " Part #2: " . json_encode(array_slice($array, $part, $part)) . " Part #3: " . json_encode(array_slice($array, $part * 2));
return merge(mergeSort(array_slice($array, 0, $part)), mergeSort(array_slice($array, $part, $part)), mergeSort(array_slice($array, $part * 2)));
}
function mergeSort(&$list, $first, $last)
{
if ($first < $last) {
//実施条件(分割できる事。)これがないと再帰が終わらない。
$center = intval(($first + $last) / 2);
$p = 0;
$j = 0;
$k = $first;
$tmp = null;
//待避配列
//前半部分をソートする
mergeSort($list, $first, $center);
//後半部分をソートする
mergeSort($list, $center + 1, $last);
//ここから前半部分と後半部分を比較して一つにする
//ソート済みの前半部分を待避配列に全て保存する
for ($i = $first; $i <= $center; $i++) {
$tmp[$p++] = $list[$i];
}
//$iが対象配列の最後まで行って、$tmp配列を全て調べ終わるまで行う
//$iは$center + 1から。つまり右側と左側($tmp)の比較
//$pも$center + 1。
//$jは0から
//$kも0から (再帰で使う時は$first)
while ($i <= $last && $j < $p) {
if ($tmp[$j] <= $list[$i]) {
//前半部分の配列が後半部分よりも小さい時
//そのまま対象配列に前半部分の値を保存
$list[$k] = $tmp[$j];
//ポインタは各々増やす
$k++;
$j++;
} else {
//後半部分のほうが小さい時
//対象配列に後半部分の値を入れる。
//前半部分の配列は$tmp配列にコピーしているので上書きでOK
$list[$k] = $list[$i];
//ポインタを各々増やす
$k++;
$i++;
}
}
//余っている待避配列があれば、全て並び替えの対象配列に追加する
while ($j < $p) {
$list[$k++] = $tmp[$j++];
}
}
}
function mergeSort(array $arr)
{
$arrCount = count($arr);
if ($arrCount <= 1) {
return $arr;
}
$firstHalf = mergeSort(array_slice($arr, 0, $arrCount / 2));
$secondHalf = mergeSort(array_slice($arr, $arrCount / 2));
$resultArr = [];
while (!empty($firstHalf) && !empty($secondHalf)) {
if ($firstHalf[0] <= $secondHalf[0]) {
$resultArr[] = array_shift($firstHalf);
} elseif ($secondHalf[0] < $firstHalf[0]) {
$resultArr[] = array_shift($secondHalf);
}
}
$resultArr = array_merge($resultArr, empty($firstHalf) ? $secondHalf : $firstHalf);
return $resultArr;
}
function mergeSort($arr)
{
if (count($arr) > 1) {
$middleVal = floor(count($arr) / 2);
$arr1 = mergeSort(array_slice($arr, 0, $middleVal));
$arr2 = mergeSort(array_slice($arr, $middleVal, count($arr)));
$counter1 = $counter2 = 0;
for ($i = 0; $i < count($arr); $i++) {
if ($counter1 == count($arr1)) {
$arr[$i] = $arr2[$counter2];
$counter2++;
} elseif ($counter2 == count($arr2) or $arr1[$counter1] < $arr2[$counter2]) {
$arr[$i] = $arr1[$counter1];
$counter1++;
} else {
$arr[$i] = $arr2[$counter2];
$counter2++;
}
}
}
return $arr;
}
/**
* Stable, good for linked list
* can be implemented parallel
* @param array $myArray
*/
function mergeSort(array $myArray)
{
if (count($myArray) < 2) {
return $myArray;
} else {
if (count($myArray) === 2) {
if ($myArray[0] > $myArray[1]) {
return [$myArray[1], $myArray[0]];
}
return $myArray;
}
}
$midPoint = ceil(count($myArray) / 2);
$firstArray = mergeSort(array_slice($myArray, 0, $midPoint));
$secondArray = mergeSort(array_slice($myArray, $midPoint, count($myArray)));
$merged = [];
while ($firstArray && $secondArray) {
$firstVal = array_shift($firstArray);
$secondVal = array_shift($secondArray);
$first = $firstVal < $secondVal ? $firstVal : $secondVal;
$second = $firstVal < $secondVal ? $secondVal : $firstVal;
$last = end($merged);
if ($first < $last) {
list($merged[count($merged) - 1], $first) = [$first, $merged[count($merged) - 1]];
}
$merged[] = $first;
$merged[] = $second;
}
if ($firstArray) {
$merged[] = array_shift($firstArray);
}
return $merged;
}
/**
* The famous merge sort algorithm implementation
*
* $data is an array formatted as follow (with $i as an index):
* list($song_id, $usr_id, $country_code) = $data[$i];
*
* @param $data, a multidimensional array containing the log data
* @param $comparator1, the first comparator index (0: song_id, 1: usr_id, 2: country_code)
* @param $comparator2, the second comparator index (0: song_id, 1: usr_id, 2: country_code)
*/
function mergeSort($data, $comparator1, $comparator2)
{
if (count($data) <= 1) {
return $data;
}
$mid = count($data) / 2;
$left = array_slice($data, 0, $mid);
$right = array_slice($data, $mid);
$left = mergeSort($left, $comparator1, $comparator2);
$right = mergeSort($right, $comparator1, $comparator2);
return merge($left, $right, $comparator1, $comparator2);
}
function mergeSort(&$arr, $from, $end)
{
#切分数组直到数组元素只剩下一个
if ($from < $end) {
$mid = floor(($from + $end) / 2);
mergeSort($arr, $from, $mid);
mergeSort($arr, $mid + 1, $end);
#合并数组
$tempArr = array();
$leftInx = $from;
$rightInx = $mid + 1;
#合并左右两部,直到左边或右边部分全部排入临时数组
while ($leftInx <= $mid && $rightInx <= $end) {
if ($arr[$leftInx] < $arr[$rightInx]) {
$tempArr[] = $arr[$leftInx++];
} else {
$tempArr[] = $arr[$rightInx++];
}
}
#处理没有排完的一部分的剩下元素,因为待合并的部分是有序数组,剩下的元素直接全部加入临时数组
while ($leftInx <= $mid) {
$tempArr[] = $arr[$leftInx++];
}
while ($rightInx <= $end) {
$tempArr[] = $arr[$rightInx++];
}
#用临时数组的值替换掉原数组的值
array_splice($arr, $from, $end - $from + 1, $tempArr);
}
}
$tmp[] = $arr[$i];
$i++;
}
while ($j <= $high) {
$tmp[] = $arr[$j];
$j++;
}
$len = count($tmp);
for ($k = 0; $k < $len; $k++) {
$arr[$low + $k] = $tmp[$k];
}
}
$arr = array(2, 3, 4, 6, 5, 9, 8, 7, 1, 0);
echo "排序之前：";
print_r($arr);
echo "</br>";
mergeSort($arr);
echo "排序之后：";
print_r($arr);
?>
</body>
</html>
/*归并排序
Order Results
排序前：Array ( [0] => 2 [1] => 3 [2] => 4 [3] => 6 [4] => 5 [5] => 9 [6] => 8 [7] => 7 [8] => 1 [9] => 0 )
排序后：Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 [5] => 5 [6] => 6 [7] => 7 [8] => 8 [9] =>9 )*/
