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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| <?php | ||
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| /** | ||
| * 选择排序 | ||
| * 工作原理是每次从待排序的元素中的第一个元素设置为最小值， | ||
| * 遍历每一个没有排序过的元素，如果元素小于现在的最小值， | ||
| * 就将这个元素设置成为最小值，遍历结束就将最小值和第一个没有排过序交换位置， | ||
| * 这样的遍历需要进行元素个数-1次 | ||
| * 这是一个不稳定的排序算法(排序后相对次序改变了) | ||
| * 对于选择排序如何找到最小元是关键 所以我们需要使用堆排序 | ||
| */ | ||
| require_once __DIR__ . '/../uniqueRandom.php'; | ||
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| function selectionSort(&$arr) | ||
| { | ||
| $count = count($arr); | ||
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| //重复元素个数-1次 | ||
| for ($j = 0; $j <= $count - 1; $j++) { | ||
| //把第一个没有排过序的元素设置为最小值 | ||
| $min = $arr[$j]; | ||
| //遍历每一个没有排过序的元素 | ||
| for ($i = $j + 1; $i < $count; $i++) { | ||
| //如果这个值小于最小值 | ||
| if ($arr[$i] < $min) { | ||
| //把这个元素设置为最小值 | ||
| $min = $arr[$i]; | ||
| //把最小值的位置设置为这个元素的位置 | ||
| $minPos = $i; | ||
| } | ||
| } | ||
| //内循环结束把最小值和没有排过序的元素交换 | ||
| list($arr[$j], $arr[$minPos]) = [$min, $arr[$j]]; | ||
| } | ||
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| } | ||
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| $arr = uniqueRandom(1, 100000, 5000); | ||
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| $start = microtime(true); | ||
| selectionSort($arr); | ||
| $end = microtime(true); | ||
| $used = $end - $start; | ||
| echo "used $used s" . PHP_EOL; | ||
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| //used 1.1448910236359 s |
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