PHP实现 bitmap 位图排序 求交集

2014年12月16日 17:15:09

初始化一串全为0的二进制;

现有一串无序的整数数组;

如果整数x在这个整数数组当中,就将二进制串的第x位置为1;

然后顺序读取这个二进制串,并将为1的位转换成整数,顺序存放到新的集合中,就是排好序的了

排序代码:

     function sort()
     {
         // var_dump(PHP_INT_MAX, PHP_INT_SIZE);
         // int 9223372036854775807
         // int 8
         $bitmap = array_fill(0, 50, 0); //申请一个整形数组, 50个元素, 初始化为整数0
         $int_bit_size = PHP_INT_SIZE * 8; //$bitmap中每个整形的二进制位数 (本例中int = 8*8 = 64bit; $bitmap数组一共50*64 = 3200个bit位),也就是说能为最大值小于等于3200的整数集合排序
         $a = array(1,4,3,50,34,60,100,88,200,150,300); //定义一个乱序的数组

         //扫描$a中的每一个数, 将其转换为 x*64 + y
         foreach ($a as $k => $v) {
             $shang = $v / $int_bit_size;
             $yushu = $v % $int_bit_size;

             $offset = 1 << $yushu;

             $bitmap[$shang] = $bitmap[$shang] | $offset;//将bit位置为1
         }

         //将$bitmap中的bit位依次还原为整数输出,即可得到排序后的数组
         $b = array();
         foreach ($bitmap as $k => $v) {
             for ($i = 0; $i < $int_bit_size; $i++) {
                 $tmp = 1 << $i;
                 $flag = $tmp & $bitmap[$k];

                 // $b[] = $flag ? $k * $int_bit_size + $i : false;
                 if ($flag) {
                     $b[] =  $k * $int_bit_size + $i;
                 }
             }
         }

         var_dump($b);exit;
     }
 // 浏览器输出:
 array
   0 => int 1
   1 => int 3
   2 => int 4
   3 => int 34
   4 => int 50
   5 => int 60
   6 => int 88
   7 => int 100
   8 => int 150
   9 => int 200
   10 => int 300

求交集代码:

生成两个bitmap -> 循环两个bitmap 与操作 生成一个新的bitmap -> 还原bitmap为数字

public function sort($a = array())
    {
        // var_dump(PHP_INT_MAX, PHP_INT_SIZE);
        // int 9223372036854775807
        // int 8
        $bitmap = array_fill(0, 50, 0); //申请一个整形数组, 50个元素, 初始化为整数0
        $int_bit_size = PHP_INT_SIZE * 8; //$bitmap中每个整形的二进制位数 (本例中int = 8*8 = 64bit; $bitmap数组一共50*64 = 3200个bit位)
        // $a = array(1,4,3,50,34,60,100,88,200,150,300); //定一个乱序的数组

        //扫描$a中的每一个数, 将其转换为 x*64 + y
        foreach ($a as $k => $v) {
            $shang = $v / $int_bit_size;
            $yushu = $v % $int_bit_size;

            $offset = 1 << $yushu;

            $bitmap[$shang] = $bitmap[$shang] | $offset;//将bit位置为1
        }

        return $bitmap;
    }

    public function intersect()
    {
        $int_bit_size = PHP_INT_SIZE * 8;

        $a = array(1,4,3,50,34,60,100,88,200,150,300);
        $b = array(1,5,3,50,34,55,100,87,222,150,300);

        $bit_a = $this->sort($a);
        $bit_b = $this->sort($b);

        $c = array();
        foreach ($bit_a as $k => $v) {
            $c[$k] = $bit_a[$k] & $bit_b[$k]; //二进制 & 计算求交集
        }

        $d = array();
        foreach ($c as $k => $v) {
            for ($i = 0; $i < $int_bit_size; $i++) {
                $tmp = 1 << $i;
                $flag = $tmp & $c[$k];

                // $b[] = $flag ? $k * $int_bit_size + $i : false;
                if ($flag) {
                    $d[] =  $k * $int_bit_size + $i;
                }
            }
        }

        var_dump($d);exit;

    }
浏览器输出:
array
  0 => int 1
  1 => int 3
  2 => int 34
  3 => int 50
  4 => int 100
  5 => int 150
  6 => int 300

参考:

http://kevinbest0702.blog.163.com/blog/static/85409746201291484128939/

http://www.cnblogs.com/dolphin0520/archive/2011/10/19/2217369.html