本文實(shí)例講述了PHP實(shí)現(xiàn)bitmap位圖排序求交集的方法。分享給大家供大家參考，具體如下：
初始化一串全為0的二進(jìn)制;
現(xiàn)有一串無序的整數(shù)數(shù)組;
如果整數(shù)x在這個(gè)整數(shù)數(shù)組當(dāng)中,就將二進(jìn)制串的第x位置為1;
然后順序讀取這個(gè)二進(jìn)制串,并將為1的位轉(zhuǎn)換成整數(shù),順序存放到新的集合中,就是排好序的了
排序代碼:
function sort(){ // var_dump(PHP_INT_MAX, PHP_INT_SIZE); // int 9223372036854775807 // int 8 $bitmap = array_fill(0, 50, 0); //申請(qǐng)一個(gè)整形數(shù)組, 50個(gè)元素, 初始化為整數(shù)0 $int_bit_size = PHP_INT_SIZE * 8; //$bitmap中每個(gè)整形的二進(jìn)制位數(shù) (本例中int = 8*8 = 64bit; $bitmap數(shù)組一共50*64 = 3200個(gè)bit位),也就是說能為最大值小于等于3200的整數(shù)集合排序 $a = array(1,4,3,50,34,60,100,88,200,150,300); //定義一個(gè)亂序的數(shù)組 //掃描$a中的每一個(gè)數(shù), 將其轉(zhuǎn)換為 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] | $offset;//將bit位置為1 } //將$bitmap中的bit位依次還原為整數(shù)輸出,即可得到排序后的數(shù)組 $b = array(); foreach ($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;}瀏覽器輸出:
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
求交集代碼:
public function sort($a = array()){ // var_dump(PHP_INT_MAX, PHP_INT_SIZE); // int 9223372036854775807 // int 8 $bitmap = array_fill(0, 50, 0); //申請(qǐng)一個(gè)整形數(shù)組, 50個(gè)元素, 初始化為整數(shù)0 $int_bit_size = PHP_INT_SIZE * 8; //$bitmap中每個(gè)整形的二進(jìn)制位數(shù) (本例中int = 8*8 = 64bit; $bitmap數(shù)組一共50*64 = 3200個(gè)bit位) // $a = array(1,4,3,50,34,60,100,88,200,150,300); //定一個(gè)亂序的數(shù)組 //掃描$a中的每一個(gè)數(shù), 將其轉(zhuǎn)換為 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;//將bit位置為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]; //二進(jìn)制 & 計(jì)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;}瀏覽器輸出:
array
0 => int 1
1 => int 3
2 => int 34
3 => int 50
4 => int 100
5 => int 150
6 => int 300
希望本文所述對(duì)大家PHP程序設(shè)計(jì)有所幫助。
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