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  今天看到了一道题,觉得比较有意思

$n = 20;for($i = 0; $i < $n; $i--) {    var_dump('-');}

说是,上面那段代码修改或是增加一处,循环体内执行二十次,明眼人都看出来,上述代码是死循环的,下面是几个方法
1、
$n =20;for ($i = 0; -$i < $n; $i --) {    var_dump('-');}

2、
$n = 20;for ($i = 0; $i < $n; $i ++) {    var_dump('-');}

3、
$n =20;for ($i = 0; $i < $n; $n --) {    var_dump('-');}

不过听说还有好多解法,希望知道的朋友能够列举出来,开开眼界!!!


回复讨论(解决方案)

$n = 20;
for($i = 40; $i      var_dump('-');
}

楼上的朋友试了没有,知道for语句是怎么执行的么

$n =20; for ($i = 0; $n < $i; $n --) {     var_dump('-');   }
 

感谢版主回答,不过怎么执行显示不出来呢,而且改也不止一处

感谢版主回答,不过怎么执行显示不出来呢,而且改也不止一处

怎么不止改一处了?
那2个对换不就只是改一处么?,又不是限定值改一个变量

楼上的朋友试了没有,知道for语句是怎么执行的么

没有,你说是死循环就考虑for括号里面的东西了,没看别的地方。
再说我觉得从40减到20也没啥问题嘛

呵呵,看错了,你原来后面那个是i啊
还以为后面一个是n呢

引用 2 楼 molaifeng 的回复:楼上的朋友试了没有,知道for语句是怎么执行的么

没有,你说是死循环就考虑for括号里面的东西了,没看别的地方。
再说我觉得从40减到20也没啥问题嘛

呵呵,关键是那样弄的话,for循环就不执行了,到了判断那里就过去了

$n =20; for($i = 0; $i*($i+$n) < $n; $i--) {    var_dump('-');}

$n = 20;
for($i = 0; $i      var_dump('-');
    $n=$n-2;
}

$n =20; for($i = 0; $i < $n*($i+$n); $i--) {    var_dump('-');}


这些都可以id,会是改或加都可以,那就可以运用很多公式放在条件那里的

添加或修改一位哦,楼上的朋友,你这添加了一句

$n = 20;
for($i = 0; $i      var_dump('-');
}

添加或修改一位哦,楼上的朋友,你这添加了一句

说的是添加或修改一处,不是添加一位

这个概念差远了,如果只能修改一个变量或者加一个变量,那可就差远了

$n =20;
for ($i = 0; -$i      var_dump('-');
 
}

$n = 20; for($i = 0; ($i*$i) < $n; $i--) {         var_dump('-');}

$n = 20; for($i = 0; abs($i) < $n; $i--) {         var_dump('-');}

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