C++ 从链表数组访问节点数据

我正在做一个相当冗长的任务，目前有一个致命的问题。我无法正确实现对存储在指针中的链表中的数据的节点访问

起初，我得到了一个分割错误，但经过一些研究，如，我能够澄清这一点。现在我已经修复了分段错误，我的代码甚至无法编译

我已经“cout”调试到我知道问题存在于我的

Cache.h

文件中，特别是在我尝试将新节点

p

设置为某个数组值的起始节点时，在我的

addElement

函数中。试图清晰地评论

因为我的数组是一个链表数组，所以它本质上是一个指针数组。类型声明为

节点*

。我觉得p应该是指向指针的指针，因为它不是任何列表的一部分，需要通过数组访问数据。我已经尝试了大约一百万个指针和指向指针的指针的组合，但是没有任何东西允许我再次编译。我已经完成了所有我知道怎么做的调试，所以我求助于你

我将在下面发布代码<代码>命令。在中，基本上包含我将要使用的文件的名称

A.data

是我正在对其数据进行操作的文件（

min

for ex）

Process.cpp

包含了我的主要功能，以及基本操作，而

Cache.h

的存在就是为了拥有这个指针

由于问题肯定存在于

Cache.h

中，因此我将首先发布该问题，然后发布所有其他问题。同样，错误位置应该是显而易见的。希望这是我对指针的理解上的一些错误和一个简单的解决方法

谢谢

Cache.h`

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

//CLASS TO STORE SIMPLE "CACHE"

class Cache
{


 private:

  struct node
  {
    double val;
    string cacheName;
    string cacheOp;
    node * next;
  };

  node * cacheArr[26];





 public:

    //CONSTRUCTOR, SET VALUES OF cacheArr TO NULL
    Cache()
      {
        for (int i = 0; i < 26; i++)
          {
            cacheArr[i] = new node;
          }
      }



    //ADD AN ELEMENT TO CACHE
    void addElement (string file, string op, double value)
    {
      node** p;
      char ch = file[0];
      //convert
      int alphaNum  = (int)(ch - 'A');

      cout << "\nALPHA NUM = " << alphaNum << " -- ch = " << ch << endl;

      cout << "TEST PRE";
      /*

        HERE LIES THE PROBLEM
        vvvvvvvvvvvvvvvvvvvvv

      */
      p* = cacheArr[alphaNum];
 cout << "\nTEST";

      if (p == NULL)
        {
          //no values starting with 'ch' have been used
          //create new node

          p->cacheName = file;
          p->cacheOp = op;
          p->val = value;
          p->next = NULL;
          return;
        }
      else if (p->next == NULL)
        {
          //list has  one value, add to list if so
              p = p->next;
              p->cacheName = file;
              p->cacheOp = op;
              p->val = value;
              p->next = NULL;
              return;
        }

      //list has 2+ elements
      //bring p to last element
      while(p!=NULL)
            {
              p = p->next;
            }
`          //p is at end of list

          p->cacheName = file;
          p->cacheOp = op;
          p->val = value;
          p->next = NULL;


          return;
    }


    //checks to see if file already in cache
    bool checkCache(string file, string op)
    {
      char ch = file[0];
      int numAlpha = (int)(ch - 'A' + 1);
      node* p = cacheArr[numAlpha];
      if(p == NULL)
        {
          return false;
        }
      while(p!=NULL)
        {
          if(p->cacheName == file && p->cacheOp == op)
            {
              return true;
            }
          p = p->next;
        }
      return false;
    }



    //RETURNS VALUE OF CACHE
    double getVal(string file, string op)
    {
      char ch = file[0];
      int numAlpha = (int)(ch - 'A' + 1);
      node * p = cacheArr[numAlpha];
      while (p!=NULL)
        {
          if(p->cacheName == file && p->cacheOp == op)
            {
              return p->val;
            }
          p = p->next;
        }
      return 0;
    }




};

    //END OF CLASS

A.数据`

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`

忘了，我得到的错误代码`

[dilleyj@cs1 HW6]$ g++ -Wall -o process Process.cpp
In file included from Process.cpp:6:0:
Cache.h: In member function ‘void Cache::addElement(std::string, std::string, double)’:
Cache.h:59:7: error: expected primary-expression before ‘=’ token
    p* = cacheArr[alphaNum];
       ^
Cache.h:67:8: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheName = file;
        ^
Cache.h:68:8: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheOp = op;
        ^
Cache.h:69:8: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->val = value;
        ^
Cache.h:70:8: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->next = NULL;
        ^
Cache.h:73:16: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
    else if (p->next == NULL)
                ^
Cache.h:76:14: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
       p = p->next;
              ^
Cache.h:77:9: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->cacheName = file;
         ^
Cache.h:78:9: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->cacheOp = op;
         ^
Cache.h:79:9: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->val = value;
         ^
Cache.h:80:9: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->next = NULL;
         ^
Cache.h:88:13: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p = p->next;
             ^
Cache.h:93:8: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheName = file;
        ^
Cache.h:94:8: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheOp = op;
        ^
Cache.h:95:8: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->val = value;
        ^
`

---

至少有两个问题

p*=cacheArr[alphaNum]应该是
*p=cacheArr[alphaNum]

然后，在同一个函数中，
p->
应该是
（*p）->
，因为
p
是指向指针的指针。
我已经调试过，我提供了一个示例，我已经找到了错误的确切位置，现在我想知道是否有人可以看一眼，看看它是否只是实现错误。如果我知道C++中的任何一条代码，我就可以认识到这个问题是错误的。在我发表这篇文章后不到10秒，你就发表了这篇评论。我觉得我自己已经做了足够多的工作，值得在一分钟的时间里请求一个善良的灵魂快速地看一眼。它不应该是星号p而不是星号p吗？@JeffreyDilley“你在我发表这篇文章后不到10秒就发表了这条评论”当然，这是我经常使用的股票评论。乍一看，不清楚您是否遇到了基本的编译器错误，也不清楚您是否缺乏调试工作，因为这是VLQ问题中常见的问题。您应该学习如何正确解释编译器错误。在这里问这样的问题没有多大价值。@JeffreyDilley请采用统一的格式。有时你不放空格，有时放，甚至两次。新行也是这样。缩进是很奇怪的。像你所关心的那样编写代码会让你成为一个更好的程序员。除非你想让强迫症患者受苦我不再看代码了。。。p*=cacheArr[alphaNum]；还是您打算取消对赋值运算符的引用？
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[dilleyj@cs1 HW6]$ g++ -Wall -o process Process.cpp
In file included from Process.cpp:6:0:
Cache.h: In member function ‘void Cache::addElement(std::string, std::string, double)’:
Cache.h:59:7: error: expected primary-expression before ‘=’ token
    p* = cacheArr[alphaNum];
       ^
Cache.h:67:8: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheName = file;
        ^
Cache.h:68:8: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheOp = op;
        ^
Cache.h:69:8: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->val = value;
        ^
Cache.h:70:8: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->next = NULL;
        ^
Cache.h:73:16: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
    else if (p->next == NULL)
                ^
Cache.h:76:14: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
       p = p->next;
              ^
Cache.h:77:9: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->cacheName = file;
         ^
Cache.h:78:9: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->cacheOp = op;
         ^
Cache.h:79:9: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->val = value;
         ^
Cache.h:80:9: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p->next = NULL;
         ^
Cache.h:88:13: error: request for member ‘next’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
      p = p->next;
             ^
Cache.h:93:8: error: request for member ‘cacheName’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheName = file;
        ^
Cache.h:94:8: error: request for member ‘cacheOp’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->cacheOp = op;
        ^
Cache.h:95:8: error: request for member ‘val’ in ‘* p’, which is of pointer type ‘Cache::node*’ (maybe you meant to use ‘->’ ?)
     p->val = value;
        ^
`