我在使用某些代码时遇到问题，我必须添加将人员输入到我的结构链接列表中的选项。我可以使用整数作为标识符将人添加到第一个节点，但是当我添加另一个节点时，它只要求整数而不要求其他详细信息。这是我的代码:
#include <stdio.h>
#include <stdlib.h>
#include "linkedlist.h" /* conatins structure definition */
/* Function Prototypes
Note that variable names have been removed as they are
not actually required - they are optional
*/
int fnTotalList(struct listnode *);
struct listnode *fnAddItem(struct listnode *, int);
void fnPrintList(struct listnode *);
int fnMenu(void);
struct listnode *fnRemoveEndItem(struct listnode *, int *);
struct listnode *fnRemoveStartItem(struct listnode *, int *);
void fnSearchList(struct listnode *, int);
int main(int argc, char *argv[])
{
struct listnode *ptrHead = NULL;
struct listnode *ptrTemp = NULL;
int nChoice = 0;
int nRun = 1;
int nItem = 0;
while(nRun)
{
nChoice = fnMenu();
switch(nChoice)
{
case 1: /* Add an item */
printf("Please enter an integer : ");
scanf("%d", &nItem);
ptrHead = fnAddItem(ptrHead,nItem);
break;
case 2: /* Print the list */
fnPrintList(ptrHead);
printf("The list total is %d\n", fnTotalList(ptrHead));
break;
case 3: /* Remove an end item */
ptrHead = fnRemoveEndItem(ptrHead, &nItem);
if(nItem == -9999)
printf("Nothing to remove - empty list\n\n");
else
printf("The removed value is %d\n\n", nItem);
break;
case 4: /* Remove a start item */
ptrHead = fnRemoveStartItem(ptrHead, &nItem);
if(nItem == -9999)
printf("Nothing to remove - empty list\n\n");
else
printf("The removed value is %d\n\n", nItem);
break;
case 5: /* Search the list */
printf("Please enter the search value : ");
scanf("%d", &nItem);
fnSearchList(ptrHead, nItem);
break;
case 6: /* Exit program */
nRun = 0; /* set to zero to stop the while loop */
break;
}
}
return 0;
}
struct listnode *fnAddItem(struct listnode *ptrH, int nNumber)
{
struct listnode *ptrTemp = NULL;
if(ptrH == NULL)
{
/* Special case - list empty */
ptrH = (struct listnode *)malloc(sizeof(struct listnode));
if(ptrH == NULL)
{
printf("Adding to empty list - malloc has failed\n");
exit(1);
}
/* malloc has worked - set values */
(*ptrH).nVal = nNumber;
printf("Please Enter First , Second & Last Name : ");
scanf("%s %s %s",(*ptrH).arcFirstName,(*ptrH).arcMiddleName,(*ptrH).arcLastName);
printf("Please Enter Sex M or F : ");
scanf("%s", (*ptrH).cSex);
printf("DOB - DDMMYYYY\n");
scanf("%i %i %i", &nD, &nM, &nY);
(*ptrH).strDOB.nDay=nD;
(*ptrH).strDOB.nMonth=nM;
(*ptrH).strDOB.nYear=nY;
ptrH->ptrNext = NULL; /* This is important as it signals
the last node within the list */
}
else
{
/* There are items already in the list
need to locate the end - use a while loop
to step through looking for ptrNext to
equal NULL */
ptrTemp = ptrH; /* Use a temp pointer */
while(ptrTemp->ptrNext != NULL)
{
/* As ptrNext has a value there is a node
hanging off it */
ptrTemp = ptrTemp->ptrNext;
}
/* ptrTemp is now pointing at the last node
within the list
Now, create a new node that "hangs off"
ptrNext within this last node */
ptrTemp->ptrNext = (struct listnode *)malloc(sizeof(struct listnode));
if(ptrTemp->ptrNext == NULL)
{
printf("Adding to end of list - malloc has failed\n");
exit(1);
}
ptrTemp->ptrNext->nVal = nNumber;
ptrTemp->ptrNext->ptrNext = NULL;
}
return ptrH; /* This is really only needed when adding the first item
to the list - but have to do it in all cases to avoid
error messages */
}
int fnMenu(void)
{
int nChoice;
printf("Choices menu\n\n");
printf("1.\tAdd an item\n");
printf("2.\tPrint list\n");
printf("3.\tRemove an end item\n");
printf("4.\tRemove a start item\n");
printf("5.\tSearch for a value\n");
printf("6.\tQuit\n\n");
printf("Please enter a choice :");
scanf("%d", &nChoice);
return nChoice;
}
void fnPrintList(struct listnode *ptrH)
{
if(!ptrH)
{
printf("\n\n\tEmpty list\n");
}
else
{
while(ptrH)
{
printf("%d\n", ptrH->nVal);
ptrH = ptrH->ptrNext;
}
printf("\nEnd of list\n\n");
}
}
struct listnode *fnRemoveEndItem(struct listnode *ptrH, int *ptrNum)
{
/* There are two special cases ...
1. When the list is empty
2. When there is only one node within the list
*/
struct listnode *ptrTemp = NULL;
if(!ptrH)
{
/* The list is empty */
*ptrNum = -9999; /* A value to signal empty list */
}
else if(!ptrH->ptrNext)
{
/* There is only one node in the list
as ptrNext within the first node
is NULL
*/
*ptrNum = ptrH->nVal;
free(ptrH); /* This releases the memory allocated
by malloc() back to the heap */
ptrH = NULL; /* As this was the last item to remove
need to return NULL so that ptrHead
is set to NULL */
}
else
{
/* There are more than one nodes in the list,
need to step through to find the last but
one node
*/
ptrTemp = ptrH;
while(ptrTemp->ptrNext->ptrNext)
{
ptrTemp = ptrTemp->ptrNext;
}
/* ptrTemp is now pointing to the last but
one node so can delete the last one
*/
*ptrNum = ptrTemp->ptrNext->nVal;
free(ptrTemp->ptrNext);
ptrTemp->ptrNext = NULL; /* Set to NULL as this is
now the last node
*/
}
return ptrH;
}
struct listnode *fnRemoveStartItem(struct listnode *ptrH, int *ptrNum)
{
struct listnode *ptrTemp = NULL;
if(!ptrH)
{
/* Empty list */
*ptrNum = -9999;
return ptrH;
}
else
{
ptrTemp = ptrH->ptrNext;
*ptrNum = ptrH->nVal;
free(ptrH);
return ptrTemp;
}
}
void fnSearchList(struct listnode *ptrH, int nSearchVal)
{
struct listnode *ptrTemp = ptrH;
int nCount = 0;
if(!ptrH)
{
/* Empty List */
printf("\n\nEmpty List \n\n");
}
else
{
while(ptrTemp->ptrNext)
{
if(ptrTemp->nVal == nSearchVal)
{
printf("The value %d has been located\n", ptrTemp->nVal);
nCount++;
}
ptrTemp = ptrTemp->ptrNext;
}
if(!nCount)
printf("\t\tValue not found within the list\n");
else
printf("\t\tA total of %d were found\n", nCount);
}
printf("The list totals %d\n", fnTotalList(ptrH));
}
int fnTotalList(struct listnode *ptrH)
{
struct listnode *ptrTemp = ptrH;
int nTotal = 0;
if(ptrTemp)
{
while(ptrTemp)
{
nTotal += ptrTemp->nVal;
ptrTemp = ptrTemp->ptrNext;
}
}
return nTotal;
}
最佳答案
在函数fnAddItem中，有两种情况，一种是当指针为NULL时，即List为空，并且您正确添加了第一个节点。
另一种情况是，当已经有某个节点时，您正在遍历到最后一个节点并在那里添加一个节点，但没有要求输入。这就是为什么对于第二个节点及之后的节点，您没有其他详细信息。
在 else 部分中 malloc 后，您必须像在 if 部分中那样接受输入。
struct listnode *fnAddItem(struct listnode *ptrH, int nNumber)
{
struct listnode *ptrTemp = NULL;
if(ptrH == NULL)
{
/* Special case - list empty */
ptrH = (struct listnode *)malloc(sizeof(struct listnode));
if(ptrH == NULL)
{
printf("Adding to empty list - malloc has failed\n");
exit(1);
}
/* malloc has worked - set values */
(*ptrH).nVal = nNumber;
printf("Please Enter First , Second & Last Name : ");
scanf("%s %s %s",(*ptrH).arcFirstName,(*ptrH).arcMiddleName,(*ptrH).arcLastName);
printf("Please Enter Sex M or F : ");
scanf("%s", (*ptrH).cSex);
printf("DOB - DDMMYYYY\n");
scanf("%i %i %i", &nD, &nM, &nY);
(*ptrH).strDOB.nDay=nD;
(*ptrH).strDOB.nMonth=nM;
(*ptrH).strDOB.nYear=nY;
ptrH->ptrNext = NULL; /* This is important as it signals
the last node within the list */
}
else
{
/* There are items already in the list
need to locate the end - use a while loop
to step through looking for ptrNext to
equal NULL */
ptrTemp = ptrH; /* Use a temp pointer */
while(ptrTemp->ptrNext != NULL)
{
/* As ptrNext has a value there is a node
hanging off it */
ptrTemp = ptrTemp->ptrNext;
}
/* ptrTemp is now pointing at the last node
within the list
Now, create a new node that "hangs off"
ptrNext within this last node */
ptrTemp->ptrNext = (struct listnode *)malloc(sizeof(struct listnode));
if(ptrTemp->ptrNext == NULL)
{
printf("Adding to end of list - malloc has failed\n");
exit(1);
}
/* malloc has worked - set values */
ptrTemp->ptrNext->nVal = nNumber;
printf("Please Enter First , Second & Last Name : ");
scanf("%s %s %s",ptrTemp->ptrNext->arcFirstName,ptrTemp->ptrNext->arcMiddleName,ptrTemp->ptrNext->arcLastName);
printf("Please Enter Sex M or F : ");
scanf("%s", ptrTemp->ptrNext->cSex);
printf("DOB - DDMMYYYY\n");
scanf("%i %i %i", &nD, &nM, &nY);
ptrTemp->ptrNext->strDOB.nDay=nD;
ptrTemp->ptrNext->strDOB.nMonth=nM;
ptrTemp->ptrNext->strDOB.nYear=nY;
ptrTemp->ptrNext->ptrNext = NULL; /* This is important as it signals
the last node within the list */
}
return ptrH; /* This is really only needed when adding the first item
to the list - but have to do it in all cases to avoid
error messages */
}
尽管这是一个糟糕的设计，您应该malloc一次，获取输入并填充结构，然后将其添加到列表中的适当位置。这样你就可以省略函数中很大一部分冗余代码。
关于c - c 中的链接列表存在问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21908424/