如何计算长字符串中多个模式的出现次数？

Question

我有一个很长的字符串和一组国名。所以阵列看起来像这样：

array('Afghanistan', 'Bulgaria', 'United States', 'Bulgaria', ...) 

我需要计算每个国家出现在字符串中的次数。 有没有这样做的快速和漂亮的方式，即某种神奇的preg_match_all接收一组模式，或者我必须遍历所有国家？

Answer 1

您可以使用类似：

$country_names = array('Afghanistan', 'Bulgaria', 'United States', ...); 
$country_names_preg = "/(" . implode("|", $country_names) . ")/"; 
preg_match_all($country_names_preg, $long_string, $matches); 

//$matches will contain all of the country matches. 
$echo "found: " . implode(", ", $matches); 

// There would ideally be a check to make sure that $matches had something in it! 

Answer 2

我不认为你可以用一次调用完成它，但是当你迭代substr_count（）时，可能会比preg_ *更快。

Answer 3

我只是用一个哈希表（关联数组）和环路通过你的国家：

// Count: 
$country_names = array('Afghanistan', 'Bulgaria', 'United States', ...); 
$country_count = array(); 
foreach ($country_names as $name) { 
    $country_count[$name]++; 
} 

// Then display: 
foreach ($country_names as $name) { 
    echo "Found " . $country_count[$name] . " occurrences of $name.\n"; 
} 

Answer 4

如果你想要的东西极快的（但不是快速实施），考虑Aho Corasick's algorithm。 Here是PHP中的一个实现。

Answer 5

尝试使用substr_count http://us3.php.net/manual/en/function.substr-count.php

$yourtmplongstring = strtolower($yourlongstring); 
# the above will solve any case sensitive issues 
$country_names = array('Afghanistan', 'Bulgaria', 'United States', ...); 
$country_count = array(); 
foreach ($country_names as $name) { 
    $occurances = substr_count($name, $yourtmplongstring); 
    $country_count[$name] = $occurances; 
} 

我希望这是你要找的人！