问题描述
我想根据 partNumber 以升序插入数据。 当在main中调用该函数时,则在第一个位置成功添加节点。但是在第二次调用该函数时,插入出现了一些问题,我无法弄清楚。当我输入值(在第二次调用中)时,出现错误 进程在 8.277 秒后退出,返回值 3221225477
typedef struct part {
int partNumber;
char partName[200];
int partQuantity;
struct part *nextPart;
} Part;
Part *inventory = NULL;
void insertPart();
int
main(int argc,char *argv[])
{
insertPart();
insertPart();
insertPart();
insertPart();
return 0;
}
void
insertPart()
{
Part *tempPart,*traversePart,*swapPart;
int counter = 0;
traversePart = inventory;
tempPart = (Part *) malloc(sizeof(Part *));
printf("Enter the Part Number\n");
scanf("%d",&(tempPart->partNumber));
getchar();
printf("Enter the Part Name\n");
fgets(tempPart->partName,200,stdin);
printf("Enter the Part Quantity\n");
scanf("%d",&(tempPart->partQuantity));
getchar();
if (inventory == NULL) {
inventory = tempPart;
printf("Part added at the first position.\n");
}
else {
while (traversePart->nextPart->partNumber < tempPart->partNumber) {
counter++;
traversePart = traversePart->nextPart;
if (traversePart->nextPart == NULL) {
break;
}
}
if (counter == 0) {
swapPart = inventory;
inventory = tempPart;
tempPart->nextPart = swapPart;
}
else if (traversePart->nextPart == NULL) {
traversePart->nextPart = tempPart;
}
else {
swapPart = traversePart->nextPart;
traversePart->nextPart = tempPart;
tempPart->nextPart = swapPart;
}
}
printf("Element added at position : %d",counter);
}
解决方法
问题是 traversePart->nextPart->partNumber
traversePart->nextPart
没有指代任何东西或者它没有保存任何地址。当条件为真时插入第一个值
if (inventory == NULL) {
inventory = tempPart;
printf("Part added at the first position.\n");
}
inventory 现在保存 tempPart 的地址,但是在分配 tempPart 的值时,您永远不会为它的 nextvalue 分配地址,并且它不存在,因为您只插入了第一个值。对于第二个位置
else{
while(traversePart->nextPart!=NULL)
{
traversePart=traversePart->nextPart;
}
if(traversePart->partNumber < tempPart->partNumber){
//here you can verify conditions
traversePart->nextPart = tempPart
}
}
,
您正在混合 fgets
和 scanf
[和 getchar
]。最好只使用 fgets
,然后将 strtol
应用于数字 [或 sscanf
]。
你的链表代码有点复杂。可以简化。
这是重构后的代码。我已经提取了一些辅助函数来进行提示。
而且,我添加了列表打印。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
typedef struct part {
int partNumber;
char partName[200];
int partQuantity;
struct part *nextPart;
} Part;
Part *inventory = NULL;
void insertPart();
int getstr(char *buf,int buflen,const char *prompt);
long getnum_strtol(const char *prompt);
int
main(int argc,char **argv)
{
insertPart();
insertPart();
insertPart();
insertPart();
for (Part *cur = inventory; cur != NULL; cur = cur->nextPart)
printf("partNumber=%d partQuantity=%d partName='%s'\n",cur->partNumber,cur->partQuantity,cur->partName);
return 0;
}
void
insertPart(void)
{
Part *tempPart;
Part *cur;
Part *prev = NULL;
int counter = 0;
#if 0
tempPart = (Part *) malloc(sizeof(Part *));
#else
tempPart = malloc(sizeof(*tempPart));
#endif
tempPart->partNumber = getnum_strtol("Enter the Part Number");
getstr(tempPart->partName,sizeof(tempPart->partName),"Enter the Part Name");
tempPart->partQuantity = getnum_strtol("Enter the Part Quantity");
tempPart->nextPart = NULL;
// find the tail/end of the list
for (cur = inventory; cur != NULL; cur = cur->nextPart) {
++counter;
// insert in sorted part order
if (cur->partNumber > tempPart->partNumber)
break;
prev = cur;
}
do {
tempPart->nextPart = cur;
// insert in the middle or end of list
if (prev != NULL) {
prev->nextPart = tempPart;
break;
}
// insert in new list or before first element of existing list
tempPart->nextPart = inventory;
inventory = tempPart;
} while (0);
printf("\nElement added at position : %d\n",counter);
}
// getstr -- get a string with prompt
// RETURNS: length or (<0 -> error)
int
getstr(char *buf,const char *prompt)
{
char *cp;
int ret = 0;
// NOTE: usage of the error codes in errno.h is arbitrary
while (ret <= 0) {
// ensure buffer has enough space
if (buflen < 2) {
ret = -ENOMEM;
break;
}
// output prompt
if (prompt != NULL) {
printf("%s: ",prompt);
fflush(stdout);
}
// get a line
cp = fgets(buf,buflen,stdin);
// EOF
if (cp == NULL) {
ret = -ENODATA;
break;
}
// get buffer length
ret = strlen(buf);
// empty string
if (ret <= 0)
continue;
// point to last char
cp = &buf[ret - 1];
// ensure we got a newline -- if not,fgets had to chop the line (i.e.)
// the line is too long to fit in the buffer
if (*cp != '\n') {
ret = -ENOSPC;
break;
}
// strip the newline -- we are done
*cp = 0;
--ret;
}
return ret;
}
// getnum_strtol -- get number using strtol
long
getnum_strtol(const char *prompt)
{
int len;
int readflg = 1;
char *cp;
char buf[100];
long num = 0;
while (readflg) {
len = getstr(buf,sizeof(buf),prompt);
if (len < 0)
exit(1);
num = strtol(buf,&cp,10);
// ensure we got a least one digit
if (cp <= buf)
continue;
switch (*cp) {
case ' ':
case '\t':
case 0:
readflg = 0;
break;
default:
printf("getnum_strtol: not a valid number -- buffer '%s',invalid '%s'\n",buf,cp);
break;
}
}
return num;
}
这是我用来测试的输入文件:
37
Hex Bolt
12
28
Machine Screw
6
23
Brad Nail
1000
27
Lock Nut
300
这是程序输出:
Enter the Part Number: Enter the Part Name: Enter the Part Quantity:
Element added at position : 0
Enter the Part Number: Enter the Part Name: Enter the Part Quantity:
Element added at position : 1
Enter the Part Number: Enter the Part Name: Enter the Part Quantity:
Element added at position : 1
Enter the Part Number: Enter the Part Name: Enter the Part Quantity:
Element added at position : 2
partNumber=23 partQuantity=1000 partName='Brad Nail'
partNumber=27 partQuantity=300 partName='Lock Nut'
partNumber=28 partQuantity=6 partName='Machine Screw'
partNumber=37 partQuantity=12 partName='Hex Bolt'