gmp_popcount

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

gmp_popcountPopulation count

설명

int gmp_popcount ( GMP $a )

Get the population count.

인수

a

PHP 5.5 이전에서 GMP 수 resource나, PHP 5.6 이후에서 GMP 객체, 또는 수로 변환할 수 있는 문자열일 수 있습니다.

반환값

The population count of a, as an integer.

예제

Example #1 gmp_popcount() example

<?php
$pop1 
gmp_init("10000101"2); // 3 1's
echo gmp_popcount($pop1) . "\n";
$pop2 gmp_init("11111110"2); // 7 1's
echo gmp_popcount($pop2) . "\n";
?>

위 예제의 출력:

3
7

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User Contributed Notes 1 note

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phpmanual at headbank dot co dot uk
3 years ago
If you don't have gmp extension enabled (or don't want to use it for any reason), you can get popcount of an int using decbin() and substr_count().

<?php
$int1
= 133;
$bin1 = decbin($int1); // "10000101"
echo substr_count($bin1, "1");

// Result: 3
?>

Being a string-comparison this is far less efficient than gmp_popcount() (for which there is a dedicated instruction on most if not all modern processors), but may be handy if gmp is unavailable, or in non-performance-critical code that doesn't otherwise need it.
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