面试题一，面试题

面试题一，面试题

最近在网上看见一道面试题，随手做了一下，也作为我开始写博客的第一篇开始。

因为我最近在学习PHP，所以我就用PHP来解决它，不过天下语言是一家，其他的语言也可参照思想。题目比较简单，如下：

 

　　大厅里有100盏灯，每盏灯都编了号码，分别为1-100。每盏灯由一个开关来控制。（开关按一下，灯亮，再按一下灯灭。开关的编号与被控制的灯相同。）开始时，灯是全灭的。现在按照以下规则按动开关。
　　第一次，将所有的灯点亮。
　　第二次，将所有2的倍数的开关按一下。
　　第三次，将所有3的倍数的开关按一下。
　　以此类推。第N次，将所有N的倍数的开关按一下。
　　问第100次按完以后，大厅里还有几盏灯是亮的。

方法如 下：

<span> 1</span> <?<span>php
</span><span> 2</span> 
<span> 3</span>     <span>//</span><span>totle:总共的灯盏数，times:按动开关的次数</span>
<span> 4</span>     <span>function</span> switchLight(<span>$totle</span>,<span>$times</span><span>){
</span><span> 5</span>         <span>//</span><span>定义开关打开和关闭的状态属性</span>
<span> 6</span>             <span>$on</span>=1<span>;
</span><span> 7</span>             <span>$off</span>=-1<span>;
</span><span> 8</span>         <span>//</span><span>定义一个按动开关的动作</span>
<span> 9</span>             <span>$oc</span>=-1<span>;
</span><span>10</span>         <span>//</span><span>建立一个数组，动态存储灯盏数目,并初始化状态</span>
<span>11</span>             <span>$lights</span>=<span>array</span><span>();
</span><span>12</span>             <span>for</span>(<span>$i</span>=1;<span>$i</span><=<span>$totle</span>;<span>$i</span>++<span>){
</span><span>13</span>                 <span>$lights</span>[<span>$i</span>]=<span>$off</span><span>;
</span><span>14</span> <span>            }
</span><span>15</span>         <span>//</span><span>判断没有按动开关的情况</span>
<span>16</span>         <span>if</span>(<span>$times</span>==0<span>){
</span><span>17</span>             <span>return</span> 0<span>;
</span><span>18</span> <span>        }
</span><span>19</span>         <span>//</span><span>循环判断，并按动开关</span>
<span>20</span>         <span>for</span>(<span>$j</span>=1;<span>$j</span><=<span>$times</span>;<span>$j</span>++<span>){
</span><span>21</span>             <span>for</span>(<span>$k</span>=1;<span>$k</span><=<span>$totle</span>;<span>$k</span>++<span>){
</span><span>22</span>                 <span>if</span>(!(<span>$k</span>%<span>$j</span><span>))
</span><span>23</span>                     <span>$lights</span>[<span>$k</span>]*=<span>$oc</span><span>;
</span><span>24</span> <span>            }    
</span><span>25</span> <span>        }
</span><span>26</span>         <span>//</span><span>遍历出所有为on的灯,并存入新数组</span>
<span>27</span>         <span>$newLights</span>=<span>array</span><span>();
</span><span>28</span>         <span>for</span>(<span>$r</span>=1;<span>$r</span><=<span>$totle</span>;<span>$r</span>++<span>){
</span><span>29</span>             <span>if</span>(<span>$lights</span>[<span>$r</span>]==<span>$on</span><span>){
</span><span>30</span>                 <span>$newLights</span>[]=<span>$r</span><span>;
</span><span>31</span> <span>            }
</span><span>32</span> <span>        }
</span><span>33</span>         <span>return</span> <span>$newLights</span><span>;
</span><span>34</span>          
<span>35</span> <span>    }
</span><span>36</span>     
<span>37</span>     <span>$newLights</span>=switchLight(100,100<span>);
</span><span>38</span>     <span>echo</span> "结果有".<span>count</span>(<span>$newLights</span>)."盏灯亮,具体如下:"<span>;
</span><span>39</span>     <span>foreach</span>(<span>$newLights</span> <span>as</span> <span>$light</span><span>){
</span><span>40</span>         <span>echo</span> <span>$light</span><span>;
</span><span>41</span>         <span>echo</span> "\n"<span>;
</span><span>42</span> <span>    }
</span><span>43</span> ?>

 

　　有更好的方法，会后续更新。