如何反转字符串中的单词？

Question

其他成员已经提出/回答了这个问题,但我的情况有点不同......

问题:如何反转字符串中的单词？你可以使用strpos(),strlen(),substr()但不能使用其他非常有用的函数,比如explode(),strrev()等.

这基本上是一个面试问题所以我需要展示操纵字符串的能力.

例:

$ string ="我是个男孩"

回答:

"我是一个人"

以下是我的解决方案,花了我2​​天(叹气),但必须有更优雅的解决方案.我的代码看起来很长..

提前致谢!

我的本意:

1. get number of word
2. based on number of word count, grab each word and store into array
3. loop through array and output each word in reverse order

码:

<?php

$str = "I am a boy";

echo reverse_word($str) . "\n";

function reverse_word($input) {
    //first find how many words in the string based on whitespace
    $num_ws = 0;
    $p = 0;
    while(strpos($input, " ", $p) !== false) {
        $num_ws ++;
        $p = strpos($input, ' ', $p) + 1;
    }

    echo "num ws is $num_ws\n";

    //now start grabbing word and store into array
    $p = 0;
    for($i=0; $i<$num_ws + 1; $i++) {
        $ws_index = strpos($input, " ", $p);
        //if no more ws, grab the rest
        if($ws_index === false) {
            $word = substr($input, $p);
        }
        else {
            $length = $ws_index - $p;
            $word = substr($input, $p, $length);
        }
        $result[] = $word;
        $p = $ws_index + 1; //move onto first char of next word
    }

    print_r($result);
    //append reversed words
    $str = '';
    for($i=0; $i<count($result); $i++) {
        $str .= reverse($result[$i]) . " ";
    }
    return $str;
}

function reverse($str) {
    $a = 0;
    $b = strlen($str)-1;
    while($a < $b) {
        swap($str, $a, $b);
        $a ++;
        $b --;
    }
    return $str;
}

function swap(&$str, $i1, $i2) {
    $tmp = $str[$i1];
    $str[$i1] = $str[$i2];
    $str[$i2] = $tmp;
}

?>

Answer 1

$string = "I am a boy";

$reversed = "";
$tmp = "";
for($i = 0; $i < strlen($string); $i++) {
    if($string[$i] == " ") {
        $reversed .= $tmp . " ";
        $tmp = "";
        continue;
    }
    $tmp = $string[$i] . $tmp;    
}
$reversed .= $tmp;

print $reversed . PHP_EOL;
>> I ma a yob