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数据结构与算法之递归算法 C++和PHP实现

Jun 23, 2016 pm 01:46 PM

递归算法:就是一种直接或间接调用自身的算法。

实现过程:通过函数或者子过程来完成,在函数或者子过程中编写代码直接或间接的调用自己,即可完成递归操作。(相同类别的问题,把问题层层转换为规模缩小的子问题到最小问题有 已知条件,然后 来求解,然后得到结果逐级返回。其实也是一种循环。)

最主要体现: 小的代码量解决了非常复杂的问题

特点:

1、递归就是方法里调用自身

2、必须有一个明确的递归结束条件,称为递归出口。

3、简洁但是运行效率较低,一般不提倡使用

4、每一层的返回点、局部变量等开辟了栈来存储,递归次数过多容易造成栈溢出。


实例1:求阶乘

C++代码:

#include<iostream>int factorial(int n);int main(){    using namespace std;    int n;    cout > n;    cout   <p class="sycode">   运行结果:  </p>  <p class="sycode">      <br>  </p>  <p class="sycode">   实例2:数制转换  </p>  <p class="sycode">      <br>  </p>  <p class="sycode">   代码:  </p>  <pre name="code" class="sycode">#include<iostream>#include<cstring>void feelTheBase(char *s, int n, int sys);int main(){    using namespace std;    char s[60];    int n,sys;    cout > n;    cout > sys;    feelTheBase(s, n, sys);    cout   <p class="sycode">   运行结果:  </p>  <p class="sycode">      <br>  </p>  <p class="sycode">   <br>  </p>  <p class="sycode">   实例3: 列出某个目录下所有的子目录和文件(还可以用 scandir函数更方便 )  </p>  <p class="sycode">   PHP实现代码:  </p>  <pre name="code" class="sycode"><?phpfunction rec($dir, $lev=0){    $dh = opendir($dir); while (($file = readdir($dh)) != false) {  if ($file == '.' || $file == '..') {   continue;  }  if (is_dir($dir.'/'.$file)){      $arr = explode("/",$dir.'/'.$file);   $lev = count($arr)-3;      echo str_pad('',$lev, "--")."目录".$file."<br/>";   rec($dir.'/'.$file, $lev+1);  }else {   echo str_pad('',$lev, "--").$file."<br>";     } }  closedir($dh);}$dir = "./";rec($dir);?>
Copy after login

运行结果:



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