php – 如何反转字符串中的单词？

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_wsn";

    //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;
}

?>