算法复习---KMP算法

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<?php

$a = array("a","b","a","b","a","b","a","b","a","b","a","b", "d", "d", "a", "b", "d");
$str = array("a","b", "c", "d", "a", "b", "d");
$next = array();


nextarr($str, $next);

foreach($next as $val){
    echo $val . ",";    
}

find($next, $a, $str);
function nextarr($str, &$nexts){
    $k = -1; 
    $j = 0;
    $nexts[0] = -1; 
    while($j < count($str)){
        if($k == -1 || $str[$j] == $str[$k]){
            $j++;
            $k++;
            $nexts[$j] = $k; 
        }else{
            $k = $nexts[$k];    
        }
    }   
}


function find($next, $a, $b){

    $lena = count($a);
    $lenb = count($b);
    $i = 0;
    $j = 0;

    while($i < $lena && $j < $lenb){
        if($j == -1 || $a[$i] == $b[$j]){
            $i++;
            $j++;
        }else{
            $j = $next[$j];    
        }
    }   
    if($j == $lenb){
        echo "\n位置：" .  ($i-$j); 
    }else{
        echo "\n位置：" .  -1;
    }

}