七大常用PHP算法

1、冒泡排序

function bubble_sort($arr)
    {
        $n = count($arr);
        for ($i = 0; $i < $n; $i++) {
            for ($j = $i + 1; $j < $n; $j++) {
                if ($arr[$j] < $arr[$i]) {
                    $temp = $arr[$i];
                    $arr[$i] = $arr[$j];
                    $arr[$j] = $temp;
                }
            }
        }
        return $arr;
    }

2、归并排序

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-递归

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-非递归

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);
            }
        }
    }

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、选择排序

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;
    }