这个是从别人空间里看来的,不过自己还真从来没这么做过他们三者之间的比较,今天也学习了一下。
$arr = array();
for($i = 0; $i $arr[] = $i*rand(1000,9999);
}
function GetRunTime()
{
list($usec,$sec)=explode(" ",microtime());
return ((float)$usec+(float)$sec);
}
/*=============================================*/
$time_start = GetRunTime();
for($i = 0; $i $str = $arr[$i];
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo 'Used time of for:'.round($time_used, 7).'(s)
';
unset($str, $time_start, $time_end, $time_used);
/*=============================================*/
$time_start = GetRunTime();
while(list($key, $val) = each($arr)){
$str = $val;
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo 'Used time of while:'.round($time_used, 7).'(s)
';
unset($str, $key, $val, $time_start, $time_end, $time_used);
/*=============================================*/
$time_start = GetRunTime();
foreach($arr as $key => $val){
$str = $val;
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo 'Used time of foreach:'.round($time_used, 7).'(s)
';
?>

Kernelsecuritycheckfailure(内核检查失败)就是一个比较常见的停止代码类型,可蓝屏错误出现不管是什么原因都让很多的有用户们十分的苦恼,下面就让本站来为用户们来仔细的介绍一下17种解决方法吧。kernel_security_check_failure蓝屏的17种解决方法方法1:移除全部外部设备当您使用的任何外部设备与您的Windows版本不兼容时,则可能会发生Kernelsecuritycheckfailure蓝屏错误。为此,您需要在尝试重新启动计算机之前拔下全部外部设备。

我们知道在C语言中,'while'关键字用于定义一个循环,该循环根据传递给循环的条件来工作。现在,由于条件可以有两个值,即真或假,所以如果条件为真,则while块内的代码将被重复执行,如果条件为假,则代码将不会被执行。现在,通过将参数传递给while循环,我们可以区分while(1)和while(0),因为while(1)是一个条件始终被视为真的循环,因此块内的代码将开始重复执行。此外,我们可以说明,传递给循环并使条件为真的不是1,而是如果任何非零整数传递给while循环,则它将被视为真条件,因

Win10skype可以卸载吗是很多用户们都想知道的一个问题,因为很多的用户们发现自己电脑上的默认程序上有这个应用,担心删除后会影响到系统的运行,下面就让本站来为用户们来仔细的介绍一下Win10如何卸载SkypeforBusiness吧。Win10如何卸载SkypeforBusiness1、在电脑桌面点击Windows图标,再点击设置图标进入。2、点击“应用”。3、在搜索框中输入“Skype”,点击选中找到的结果。4、点击“卸载”。5

用for求n阶乘的方法:1、使用“for (var i=1;i<=n;i++){}”语句控制循环遍历范围为“1~n”;2、循环体中,使用“cj*=i”将1到n的数相乘,乘积赋值给变量cj;3、循环结束后,变量cj的值就n的阶乘,输出即可。

while的用法是“while 条件: 代码块”,条件是一个表达式,当条件为真时,执行代码块,然后再次判断条件是否为真,如果为真则继续执行代码块,直到条件为假为止。while是一个常用的循环控制语句,用于在满足一定条件的情况下重复执行一段代码块。

区别:1、for通过索引来循环遍历每一个数据元素,而forEach通过JS底层程序来循环遍历数组的数据元素;2、for可以通过break关键词来终止循环的执行,而forEach不可以;3、for可以通过控制循环变量的数值来控制循环的执行,而forEach不行;4、for在循环外可以调用循环变量,而forEach在循环外不能调用循环变量;5、for的执行效率要高于forEach。

在go语言中,while不是关键字,可以用for语句加break来实现while循环的效果,例“for {sum++ if sum>10{break}else{...}}”。go语言有break、default 、func、select、case、defer、go、map、else、goto、for、if、var等25个关键字。

说明1、while关键词的中文含义是当……时,即条件成立时循环执行对应的代码。while语句是循环语句中的基本结构,语法格式比较简单。执行过程2、执行while语句时,首先判断循环条件,循环条件为false时,直接执行while语句的后续代码,循环条件为true时,执行循环体代码,判断循环条件,直到循环条件不成立为止。实例inti=1;intsum=0;while(i


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