Question

我正在努力如何传递指针，以便能够根据主函数中的头部搜索链表。它意味着是包含多项式的系数和指数的结构。在allocateTerm函数中，我试图将双指针传递给另一个函数进行搜索，看看我即将创建的术语是否已经在多项式中有一个共同的术语。代码如下：

typedef struct PolyTerm{
  int iCoeff;
  int iExp;
  struct PolyTerm *pNext;
}PolyTerm;

PolyTerm *allocateTerm(int iCoeff, int iExp, PolyTerm **ppHead, PolyTerm *pCurr);
PolyTerm *findTerm(int iCoeff, int iExp, PolyTerm ***ppHead);

void main(int argc, char *argv[])
{
  PolyTerm *pPolyAHead = NULL;
  PolyTerm *pCurr = NULL;

  allocateTerm(2,3,&pPolyAHead, pCurr);
  pCurr = allocateTerm(3,4,&pPolyAHead, pCurr);
  pCurr = allocateTerm(4,5,&pPolyAHead, pCurr);
  pCurr = allocateTerm(5,6,&pPolyAHead, pCurr);

  printf("%p\n", pPolyAHead);

  for(pCurr = pPolyAHead; pCurr != NULL; pCurr=pCurr->pNext)
    printf("coeff: %d exp: %d address: %p\n", pCurr->iCoeff, pCurr->iExp, pCurr);

  PolyTerm *pPolyBHead = NULL;

  allocateTerm(7,8,&pPolyBHead, pCurr);
  pCurr = allocateTerm(9,10,&pPolyBHead, pCurr);
  pCurr = allocateTerm(11,12,&pPolyBHead, pCurr);
  pCurr = allocateTerm(13,14,&pPolyBHead, pCurr);

  for(pCurr = pPolyBHead; pCurr != NULL; pCurr=pCurr->pNext)
    printf("coeff: %d exp: %d address: %p\n", pCurr->iCoeff, pCurr->iExp, pCurr);

}

PolyTerm *allocateTerm(int iCoeff, int iExp, PolyTerm **ppHead, PolyTerm *pCurr)
{
  PolyTerm *pFind = NULL;
  if(*ppHead == NULL)
    {
      *ppHead = (PolyTerm *)malloc(sizeof(PolyTerm));
      if(*ppHead == NULL)
    {
      printf("Memory allocation error with ppHead\n");
    }
      (*ppHead)->iCoeff = iCoeff;
      (*ppHead)->iExp = iExp;
      (*ppHead)->pNext = NULL;
    }
  else
    {
      // Search to see if that exponent already exists
      printf("%p\n", *ppHead);
      pFind = findTerm(iCoeff, iExp, /*????? (some form of **pHead)*/);
      if(pFind == NULL)
    {
      PolyTerm *pNew = NULL;
      pNew = (PolyTerm *)malloc(sizeof(PolyTerm));
      if(pNew == NULL)
        printf("Memory allocation error with pNew\n");
      if((*ppHead)->pNext == NULL)
        {
          (*ppHead)->pNext = pNew;
        }
      else
        {
          pCurr->pNext = pNew;
        }
      pNew->iCoeff = iCoeff;
      pNew->iExp = iExp;
      pNew->pNext = NULL;
    }
      else
    {
      pFind->iCoeff += iCoeff;
    }
    }
}

PolyTerm *findTerm(int iCoeff, int iExp, PolyTerm ?????/*????? (some form of **pHead)*/)
{
  //printf("%p", &head);
  /*
  PolyTerm *pFind = NULL;
  for(pFind = (*ppHead); pFind != NULL; pFind = (*ppHead)->pNext)
    {
      if(pFind->iExp == iExp)
    return pFind;
    }
    return NULL;*/
}

Answer 1

我对此并不是很有信心，但无论如何都要尝试。

PolyTerm *findTerm(int iCoeff, int iExp, PolyTerm **pHead) 
{
    //process here ...
}

然后就这样称呼它：

pFind = findTerm(iCoeff, iExp, ppHead);

您必须再次向pPolyAHead传递引用，以便您仍然可以访问并比较其值。希望这会有所帮助。

Answer 2

我对你的函数做了一些修改，我不确定究竟是哪一个，但大多数原始语法都是完整的。我相信下面的代码实现了你的目标。如果缺少某些内容，请发表评论。

#include<stdlib.h>
#include<stdio.h>

typedef struct PolyTerm{
  int iCoeff;
  int iExp;
  struct PolyTerm *pNext;
}PolyTerm;

PolyTerm *allocateTerm(int iCoeff, int iExp, PolyTerm **ppHead, PolyTerm *pCurr);
PolyTerm *findTerm(int iCoeff, int iExp, PolyTerm **ppHead);

void main(int argc, char *argv[])
{
    setbuf(stdout, NULL);

    PolyTerm *pPolyAHead = NULL;
    PolyTerm *pCurr = NULL;

    pCurr = allocateTerm(2,3,&pPolyAHead, pCurr);
    //printf("%d %d %p %p\n",pCurr->iCoeff,pCurr->iExp,pPolyAHead,pCurr->pNext);
    pCurr = allocateTerm(3,4,&pPolyAHead, pCurr);
    //printf("%d %d %p\n",pCurr->iCoeff,pCurr->iExp,pCurr->pNext);
    pCurr = allocateTerm(4,5,&pPolyAHead, pCurr);
    pCurr = allocateTerm(5,6,&pPolyAHead, pCurr);

    //printf("main: %p\n", pPolyAHead);

    for(pCurr = pPolyAHead; pCurr != NULL; pCurr=pCurr->pNext)
        printf("coeff: %d exp: %d address: %p\n", pCurr->iCoeff, pCurr->iExp, pCurr);

    //exit(1);

    PolyTerm *pPolyBHead = NULL;

    allocateTerm(7,8,&pPolyBHead, pCurr);
    pCurr = allocateTerm(9,10,&pPolyBHead, pCurr);
    pCurr = allocateTerm(11,12,&pPolyBHead, pCurr);
    pCurr = allocateTerm(13,14,&pPolyBHead, pCurr);

    for(pCurr = pPolyBHead; pCurr != NULL; pCurr=pCurr->pNext)
    printf("coeff: %d exp: %d address: %p\n", pCurr->iCoeff, pCurr->iExp, pCurr);

}

PolyTerm *allocateTerm(int iCoeff, int iExp, PolyTerm **ppHead, PolyTerm *pCurr)
{
    PolyTerm *pFind = NULL;
    if(*ppHead == NULL) {
        // Occurs only on first entry.
        *ppHead = (PolyTerm *)malloc(sizeof(PolyTerm));
        if(*ppHead == NULL)
            printf("Memory allocation error with ppHead\n");

        (*ppHead)->iCoeff = iCoeff;
        (*ppHead)->iExp = iExp;
        (*ppHead)->pNext = NULL;
        return *ppHead;
    } else {
        // Search to see if that exponent already exists
        //printf("allocate: %p\n", *ppHead);
        pFind = findTerm(iCoeff, iExp, ppHead);
        if(pFind == NULL) {
            PolyTerm *pNew = NULL;
            pNew = (PolyTerm *)malloc(sizeof(PolyTerm));
            if(pNew == NULL)
                printf("Memory allocation error with pNew\n");

            if((*ppHead)->pNext == NULL)
                (*ppHead)->pNext = pNew;
            else
                pCurr->pNext = pNew;

            pNew->iCoeff = iCoeff;
            pNew->iExp = iExp;
            pNew->pNext = NULL;
        } else {
            pFind->iCoeff += iCoeff;
        }
    }
}

PolyTerm *findTerm(int iCoeff, int iExp, PolyTerm **ppHead)
{
    //printf("find: %p\n", *ppHead);

    PolyTerm *pFind;
    for(pFind = *ppHead; pFind->pNext != NULL; pFind = pFind->pNext) {
        //printf("find: iExp %d %d\n",pFind->iExp, iExp);
        if(pFind->iExp == iExp) {
            //printf("find: returned\n");
            return pFind;
        }
    }
    //printf("find: not found\n");
    return NULL;
}

输出：

coeff: 2 exp: 3 address: 001B1C28
coeff: 3 exp: 4 address: 001B1C40
coeff: 4 exp: 5 address: 001B1C58
coeff: 5 exp: 6 address: 001B1C70
coeff: 7 exp: 8 address: 001B1668
coeff: 9 exp: 10 address: 001B1680
coeff: 11 exp: 12 address: 001B1698
coeff: 13 exp: 14 address: 001B16B0

将双指针传递给另一个函数

2 个答案: