如何在大strlen值下执行这段PHP代码？

问题描述 #

这段代码在$keyy和$addrr的字符串长度较小时可正常运行，但当两者的字符串长度增大后，会出现严重的性能瓶颈（如执行时间过长、内存占用过高），该如何调整代码以适配大长度字符串的场景？

原代码 #

<?php

$con["000"] = "0";
$con["001"] = "0";
$con["010"] = "0";
$con["011"] = "1";
$con["100"] = "0";
$con["101"] = "1";
$con["110"] = "1";
$con["111"] = "1";

$keyy = [
    "0101111111101100111010110110011011111111110010000110111100111000110110010101001001111000011011000110110101101001011011000111100111000010110110111100001000111001110111010100111010010001101101000110011100101001110101110011101000100111111110110101011111101001",
    "0110101110000110101100100111001111111111001101001111110011100001100111010110101110000000010011101111111101011010001111110101011101000111101011011010010011101010101000100010111100011101010010011100000000011110010100101101110110110111100001110101101101001011",
    "1101010001110011010111100011101000100110010111100001011011101110111000000011111101011001011100011000101110011011010111010000001100000001100111000000011111011000101101101100010100011111100100001101101000111010011001100110111011101100000100111010101100110101"
];

$addrr = [
    "1100011011001000100001000011100000011010101111000001011110000100011111010101001111101001001100100111100011000001100010111010011010100010011111100000001001101010",
    "0001111011100100101010001001110100100101000110001010111010101011010111010001110010001101011100001110010011110110000011101011101101101010110100000010000000010101",
    "1001011010011000010100001010001111111011100001001100101010111110001100110001000011111010000011101001010011011001001011000101010001001110010101101011001010111110"
];

$row = count($keyy);
$coulmn = strlen($keyy[0]);

// Transpose key array
$key_arr = array();
for ($i = 0; $i < $row; $i++) {
    for ($j = 0; $j < $coulmn; $j++) {
        $key_arr[$j][$i] = $keyy[$i][$j];
    }
}

$len = count($addrr);
$len_a = strlen($addrr[0]);

// Process addresses
$addrr_n = [];
for ($ii = 0; $ii < $len; $ii++) {
    $data = '';
    for ($i = 0; $i < $len_a; $i++) {
        for ($j = 0; $j < $len_a; $j++) {
            for ($k = 0; $k < $len_a; $k++) {
                $x = $addrr[$ii][$i];
                $y = $addrr[$ii][$j];
                $z = $addrr[$ii][$k];

                // Reduce repetitive calls by grouping conditions
                $xA = (int)!$x;
                $yA = (int)!$y;
                $zA = (int)!$z;

                // Aggregate concatenations outside of the loop
                $data .= $con[$x.$y.$z]
                        .$con[$xA.$y.$z]
                        .$con[$x.$yA.$z]
                        .$con[$x.$y.$zA]
                        .$con[$xA.$yA.$z]
                        .$con[$x.$yA.$zA]
                        .$con[$xA.$y.$zA]
                        .$con[$xA.$yA.$zA];
            }
        }
    }
    $addrr_n[] = $data;
}

// Transpose the processed addrr_n
$row = count($addrr_n);
$coulmn = strlen($addrr_n[0]);
$add_arr = array();
for ($i = 0; $i < $row; $i++) {
    for ($j = 0; $j < $coulmn; $j++) {
        $add_arr[$j][$i] = $addrr_n[$i][$j];
    }
}

// Find key arrays in the result
foreach ($key_arr as $banana) {
    $encoded_banana = serialize($banana);
    $encoded_add_arr = array_map('serialize', $add_arr);

    if (in_array($encoded_banana, $encoded_add_arr)) {
        echo "Banana is in the array! Index: ";
        echo $index = array_search($encoded_banana, $encoded_add_arr);
    } else {
        echo "Banana is not in the array.";
    }
}
?>

优化方案 #

针对大长度字符串场景，核心优化方向是减少重复计算、降低内存开销、提升循环效率，具体措施如下：

1. 预计算所有可能的输出片段

$con的组合只有8种，对应的8位结果可以提前计算好，避免循环中重复拼接字符串：

// 预计算所有8位输出
$precomputed = [];
foreach ($con as $triple => $_) {
    $x = $triple[0];
    $y = $triple[1];
    $z = $triple[2];
    $xA = (int)!$x;
    $yA = (int)!$y;
    $zA = (int)!$z;
    $precomputed[$triple] = $con[$x.$y.$z]
                          .$con[$xA.$y.$z]
                          .$con[$x.$yA.$z]
                          .$con[$x.$y.$zA]
                          .$con[$xA.$yA.$z]
                          .$con[$x.$yA.$zA]
                          .$con[$xA.$y.$zA]
                          .$con[$xA.$yA.$zA];
}

2. 用数组替代字符串累加

PHP中循环拼接字符串会频繁触发内存重分配，改用数组收集所有片段，最后用implode合并，性能提升显著。

3. 提前转换为字符数组

将$addrr的每个字符串提前转为字符数组，避免循环中频繁的字符串索引操作：

$addrr_chars = array_map('str_split', $addrr);

4. 优化数组查找逻辑

原代码每次循环都序列化整个$add_arr，改为提前序列化一次并生成索引映射，直接通过键查找：

// 提前生成序列化后的索引映射
$add_index_map = [];
foreach ($add_arr as $idx => $item) {
    $add_index_map[serialize($item)] = $idx;
}

// 查找时直接检查键是否存在
foreach ($key_arr as $banana) {
    $encoded = serialize($banana);
    if (isset($add_index_map[$encoded])) {
        echo "Banana is in the array! Index: {$add_index_map[$encoded]}\n";
    } else {
        echo "Banana is not in the array.\n";
    }
}

5. 优化转置操作

转置时先将字符串转为字符数组，再进行转置，减少字符串索引的开销：

// 转置keyy数组
$key_str_chars = array_map('str_split', $keyy);
$key_arr = array();
for ($j = 0; $j < $coulmn; $j++) {
    $key_arr[$j] = [];
    for ($i = 0; $i < $row; $i++) {
        $key_arr[$j][$i] = $key_str_chars[$i][$j];
    }
}

优化后的完整代码 #

<?php

$con["000"] = "0";
$con["001"] = "0";
$con["010"] = "0";
$con["011"] = "1";
$con["100"] = "0";
$con["101"] = "1";
$con["110"] = "1";
$con["111"] = "1";

// 预计算所有8位输出片段
$precomputed = [];
foreach ($con as $triple => $_) {
    $x = $triple[0];
    $y = $triple[1];
    $z = $triple[2];
    $xA = (int)!$x;
    $yA = (int)!$y;
    $zA = (int)!$z;
    $precomputed[$triple] = $con[$x.$y.$z]
                          .$con[$xA.$y.$z]
                          .$con[$x.$yA.$z]
                          .$con[$x.$y.$zA]
                          .$con[$xA.$yA.$z]
                          .$con[$x.$yA.$zA]
                          .$con[$xA.$y.$zA]
                          .$con[$xA.$yA.$zA];
}

$keyy = [
    "0101111111101100111010110110011011111111110010000110111100111000110110010101001001111000011011000110110101101001011011000111100111000010110110111100001000111001110111010100111010010001101101000110011100101001110101110011101000100111111110110101011111101001",
    "0110101110000110101100100111001111111111001101001111110011100001100111010110101110000000010011101111111101011010001111110101011101000111101011011010010011101010101000100010111100011101010010011100000000011110010100101101110110110111100001110101101101001011",
    "1101010001110011010111100011101000100110010111100001011011101110111000000011111101011001011100011000101110011011010111010000001100000001100111000000011111011000101101101100010100011111100100001101101000111010011001100110111011101100000100111010101100110101"
];

$addrr = [
    "1100011011001000100001000011100000011010101111000001011110000100011111010101001111101001001100100111100011000