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Merge pull request #278 from wangchengtao/master

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修复 $this 引用错误, 添加相应注释, 调整部分代码, 与原文同步
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wangzheng0822 2019-03-20 10:10:09 +08:00 committed by GitHub
commit ffc5da2368
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1 changed files with 29 additions and 22 deletions
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51
php/12_sort/mergeSort.php
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@ -1,40 +1,48 @@
<?php
/*
* 归并排序
*/
$arr = [4, 5, 6, 1, 3, 2];
$length = count($arr);
$arr = [4, 5, 6, 1, 3, 2];
$length = count($arr);
$p = 0;
$r = $length - 1;
$p = 0;
$r = $length - 1;
$result = $this->mergeSort($arr, $p, $r);
$result = mergeSort($arr, $p, $r);
var_dump($result);
var_dump($result);
//递归调用,分解数组
function mergeSort(array $arr, $p, $r)
{
return mergeSortRecursive($arr, $p, $r);
}
// 递归调用函数
function mergeSortRecursive(array $arr, $p, $r)
{
// 递归终止条件
if ($p >= $r) {
return [$arr[$r]];
}
// 取 p 到 r 之间的中间位置 q
$q = (int)(($p + $r) / 2);
$left = $this->mergeSort($arr, $p, $q);
$right = $this->mergeSort($arr, $q + 1, $r);
return $this->merge($left, $right);
// 分治递归
$left = mergeSortRecursive($arr, $p, $q);
$right = mergeSortRecursive($arr, $q + 1, $r);
return merge($left, $right);
}
//合并
// 合并
function merge(array $left, array $right)
{
$tmp = [];
$i = 0;
$j = 0;
$i = $j = 0;
$leftLength = count($left);
$rightLength = count($right);
do {
@ -43,24 +51,23 @@ function merge(array $left, array $right)
} else {
$tmp[] = $right[$j++];
}
} while ($i < $leftLength && $j < $rightLength);
$start = $i;
$end = $leftLength;
$copyArr = $left;
// 判断哪个子数组中有剩余的数据
if ($j < $rightLength) {
$start = $j;
$end = $rightLength;
$copyArr = $right;
}
for (; $start < $end; $start++) {
$tmp[] = $copyArr[$start];
}
// 将剩余的数据拷贝到临时数组 tmp
do {
$tmp[] = $copyArr[$start++];
} while ($start < $end);
return $tmp;
}