这个任务已经被问过/回答了,但我最近有一个工作面试,提出了一些额外的挑战来证明我操纵字符串的能力。
问题:如何反转字符串中的单词?您可以使用strpos()
,strlen()
和substr()
,但不能使用其他非常有用的功能,例如explode()
,strrev()
等。
例子:
$string = "I am a boy"
回答:
I ma a yob
下面是我花了 2 天的工作编码尝试 [叹气],但必须有一个更优雅和简洁的解决方案。
意图:
1. get number of words
2. based on word count, grab each word and store into array
3. loop through array and output each word in reverse order
代码:
$str = "I am a boy";
echo reverse_word($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;
}