title: is there any thing wrong with include , why i cannot find strlen()
body: <pre><code>#include "Q1-VerifyUniqueCharInString.h"
  #include &lt;cstring&gt;
  #include &lt;stdio.h&gt;
  #include &lt;string.h&gt;
  
  using namespace std;
  
  
  bool isUniqueChar(string str)
  {
  
      int length=strlen(str),i=0;
      bool tab[] = new bool[length];
      if (length &gt; 0xff) {
          return false;
      }
      for (; i&lt;length;++i) {
          if (str[i]) {
              return false;
          }
          tab[str[i]]=true;
      }
      return true;
  }
  </code></pre>
  
  <p>this is my code, and i use gcc+xcode....why there is always tell me cannot find strlen, i use both cstring and string.h...</p>