下面分享一些最常見的算法，用PHP如何實現。 1、冒泡排序 ``` function?bubble_sort($arr)?{ ????$n=count($arr);????for($i=0;$i<$n-1;$i++){????????for($j=$i+1;$j<$n;$j++)?{????????????if($arr[$j]<$arr[$i])?{ ????????????????$temp=$arr[$i]; ????????????????$arr[$i]=$arr[$j]; ????????????????$arr[$j]=$temp; ????????????} ????????} ????}????return?$arr; } ``` 2、歸并排序 ``` function?Merge(&$arr,?$left,?$mid,?$right)?{ ????$i?=?$left; ????$j?=?$mid?+?1; ????$k?=?0; ????$temp?=?array();????while?($i?<=?$mid?&&?$j?<=?$right)?{????????if?($arr[$i]?<=?$arr[$j]) ????????????$temp[$k++]?=?$arr[$i++];????????else ????????????$temp[$k++]?=?$arr[$j++]; ????}????while?($i?<=?$mid) ????????$temp[$k++]?=?$arr[$i++];????while?($j?<=?$right) ????????$temp[$k++]?=?$arr[$j++];????for?($i?=?$left,?$j?=?0;?$i?<=?$right;?$i++,?$j++) ????????$arr[$i]?=?$temp[$j]; }function?MergeSort(&$arr,?$left,?$right)?{????if?($left?<?$right)?{ ????????$mid?=?floor(($left?+?$right)?/?2); ????????MergeSort($arr,?$left,?$mid); ????????MergeSort($arr,?$mid?+?1,?$right); ????????Merge($arr,?$left,?$mid,?$right); ????} } ``` 3、二分查找-遞歸 ``` function?bin_search($arr,$low,$high,$value)?{????if($low>$high)????????return?false;????else?{ ????????$mid=floor(($low+$high)/2);????????if($value==$arr[$mid])????????????return?$mid;????????elseif($value<$arr[$mid])????????????return?bin_search($arr,$low,$mid-1,$value);????????else ????????????return?bin_search($arr,$mid+1,$high,$value); ????} } ``` 4. 二分查找-非遞歸 ``` function?bin_search($arr,$low,$high,$value)?{????while($low<=$high)?{ ????????$mid=floor(($low+$high)/2);????????if($value==$arr[$mid])????????????return?$mid;????????elseif($value<$arr[$mid]) ????????????$high=$mid-1;????????else ????????????$low=$mid+1; ????}????return?false; } ``` 5、快速排序 ``` function?quick_sort($arr)?{ ????$n=count($arr);????if($n<=1)????????return?$arr; ????$key=$arr[0]; ????$left_arr=array(); ????$right_arr=array();????for($i=1;$i<$n;$i++)?{????????if($arr[$i]<=$key) ????????????$left_arr[]=$arr[$i];????????else ????????????$right_arr[]=$arr[$i]; ????} ????$left_arr=quick_sort($left_arr); ????$right_arr=quick_sort($right_arr);????return?array_merge($left_arr,array($key),$right_arr); } ``` 6、選擇排序 ``` function?select_sort($arr)?{ ????$n=count($arr);????for($i=0;$i<$n;$i++)?{ ????????$k=$i;????????for($j=$i+1;$j<$n;$j++)?{???????????if($arr[$j]<$arr[$k]) ???????????????$k=$j; ????????}????????if($k!=$i)?{ ????????????$temp=$arr[$i]; ????????????$arr[$i]=$arr[$k]; ????????????$arr[$k]=$temp; ????????} ????}????return?$arr; } ``` 7、插入排序 ``` function?insertSort($arr)?{ ????$n=count($arr);????for($i=1;$i<$n;$i++)?{ ????????$tmp=$arr[$i]; ????????$j=$i-1;????????while($arr[$j]>$tmp)?{ ????????????$arr[$j+1]=$arr[$j]; ????????????$arr[$j]=$tmp; ????????????$j--;????????????if($j<0)????????????????break; ????????} ????}????return?$arr; } ```