如何按顺序查找特定字符的出现次数

Question

我试图在一组字符中查找特定字符串的出现次数。字符串中的字母不必相邻，但必须按顺序出现。

例如，以下序列包含字符串“abc”的四次出现

序列“aabcc”

出现次数：

a a b c c

a a b c c

a a b c c

a a b c c

关于如何在不消耗字符的情况下进行匹配有什么帮助吗？我试图使用正则表达式和匹配，但我不确定它是否可能。我正在为 php 写这个

Answer 1

Demo

<?php

$sequence = "aabbcc";
$occurrences = array();

$sequences = str_split($sequence);
// dn($sequences);
$sequences_amount = array();

foreach ($sequences as $key => $char) {
    if(!isset($sequences_amount[$char])){
        $sequences_amount[$char] = 1;
    }else{
        $sequences_amount[$char]++;
    }

}

var_dump($sequences_amount);

function sequenceCount($data = array())
{
    if(!isset($data) || empty($data) || (count($data) == 0))return;

    $count = NULL;

    foreach ($data as $char => $amount) {
        if($count == NULL){
            $count = $amount;
        }else{
            $count = $count * $amount;
        }
    }

    return $count;
}

$count = sequenceCount($sequences_amount);
echo("\n\nResult:\n");

echo($count);