PHP实现四种排序
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/**
* 冒泡排序
* 按照两两比较大小,注意比较轮数和每轮比较次数;
* 假设数组有n个元素,则需要n-1轮比较;每i轮比较n-i次(即 第1轮中需要n-1次比较、第2轮中需要n-2次比较...第n-1轮中需要1次比较)
*/
function numSort($arr){
$mnt = count($arr);
if($mnt==1){
return $arr;
}
for ($i=0; $i < $mnt-1; $i++) {
for ($j=0; $j < $mnt-1-$i; $j++) {
if($arr[$j]>$arr[$j+1]){
$temp = $arr[$j];
$arr[$j] = $arr[$j+1];
$arr[$j+1] = $temp;
}
}
}
return $arr;
}
//测试
$arr = [5,2,1,1,3,1,4];
$end = numSort($arr);
echo "<pre>";
print_r($end);
过程分析:
第1轮:
第1次: Array ( [0] => 2 [1] => 5 [2] => 1 [3] => 1 [4] => 3 [5] => 1 [6] => 4 )
第2次: Array ( [0] => 2 [1] => 1 [2] => 5 [3] => 1 [4] => 3 [5] => 1 [6] => 4 )
第3次: Array ( [0] => 2 [1] => 1 [2] => 1 [3] => 5 [4] => 3 [5] => 1 [6] => 4 )
第4次: Array ( [0] => 2 [1] => 1 [2] => 1 [3] => 3 [4] => 5 [5] => 1 [6] => 4 )
第5次: Array ( [0] => 2 [1] => 1 [2] => 1 [3] => 3 [4] => 1 [5] => 5 [6] => 4 )
第6次: Array ( [0] => 2 [1] => 1 [2] => 1 [3] => 3 [4] => 1 [5] => 4 [6] => 5 )
第2轮:
第1次: Array ( [0] => 1 [1] => 2 [2] => 1 [3] => 3 [4] => 1 [5] => 4 [6] => 5 )
第2次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 3 [4] => 1 [5] => 4 [6] => 5 )
第3次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 3 [4] => 1 [5] => 4 [6] => 5 )
第4次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 1 [4] => 3 [5] => 4 [6] => 5 )
第5次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 1 [4] => 3 [5] => 4 [6] => 5 )
第3轮:
第1次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 1 [4] => 3 [5] => 4 [6] => 5 )
第2次: Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 1 [4] => 3 [5] => 4 [6] => 5 )
第3次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第4次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第4轮:
第1次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第2次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第3次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第5轮:
第1次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第2次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
第6轮:
第1次: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )
结论:
假设数组有n个元素,则需要n-1轮比较;每i轮比较n-i次(即 第1轮中需要n-1次比较、第2轮中需要n-2次比较...第n-1轮中需要1次比较)
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