我必须编写这个创建链表的代码。以下代码如下。问题是我在代码中的某个地方发生了分区，我无法弄清楚在哪里。如果有人能帮助我找到并理解（这是最重要的部分）segfault的来源，我们将不胜感激。
#include "linkedlist.h"
#include <stdio.h>
#include <stdlib.h>
/* Alloc a new node with given data. */
struct ListNode* createNode(int data) {
struct ListNode *new_node = (struct ListNode *)malloc(sizeof(struct ListNode));
new_node->data = data;
new_node->next = NULL;
return new_node;
}
/* Insert data at appropriate place in a sorted list, return new list head. */
struct ListNode* insertSorted(struct ListNode* head, int inputData)
{
struct ListNode * nextIS = NULL;
struct ListNode * newNodeIS = NULL;
struct ListNode * currIS = head;
struct ListNode * listHeadIS = currIS;
if (currIS == NULL)
{
listHeadIS = createNode(inputData);
return listHeadIS;
}
while (currIS->next != NULL)
{
nextIS = currIS->next;
if (currIS->data < inputData)
{
if (nextIS->data >= inputData)
{
nextIS->next = createNode(inputData);
newNodeIS = nextIS->next;
if (newNodeIS->data > listHeadIS->data)
{
listHeadIS = newNodeIS;
}
}
}
currIS = currIS->next;
}
return listHeadIS;
}
/* Remove data from list pointed to by headRef, changing head if necessary.
* Make no assumptions as to whether the list is sorted.
* Memory for removed node should be freed.
* Return 1 if data was present, 0 if not found. */
int removeItem(struct ListNode** headRef, int data)
{
while (*headRef && (*headRef)->data != data)
headRef = &(*headRef)->next;
if (*headRef)
{
struct ListNode *tmp = *headRef;
free(tmp);
*headRef = tmp->next;
return 1;
}
return 0;
}
/* Insert data at head of list, return new list head. */
struct ListNode* pushStack(struct ListNode* head, int data)
{
int dataPush = data;
struct ListNode * tempPush = (struct ListNode*)malloc(sizeof(struct ListNode));
tempPush->data = dataPush;
tempPush->next = head;
*head = *tempPush;
return tempPush;
}
/* Remove and return data from head of non-empty list, changing head.
* Memory for removed node should be freed. */
int popStack(struct ListNode** headRef)
{
struct ListNode * tempPop = *headRef;
int tempData;
free(tempPop);
tempData = tempPop->data;
tempPop = tempPop->next;
return tempData;
}
/* Return length of the list. */
int listLength(struct ListNode* head)
{
int count = 0;
struct ListNode* current = head;
while (current != NULL) {
count++;
current=current->next;
}
return(count);
}
/* Print list data on single line, separated with spaces and ending
* with newline. */
void printList(struct ListNode* head)
{
if (head != NULL)
{
while (head->next != NULL)
{
printf("%d\n", head->data);
head = head->next;
}
}
}
/* Free memory used by the list. */
void freeList(struct ListNode* head)
{
struct ListNode* tmp;
while (head != NULL)
{
tmp = head;
head = head->next;
free(tmp);
}
}
/* Reverse order of elements in the list */
void reverseList(struct ListNode** headRef)
{
struct ListNode * origRL = *headRef;
struct ListNode * nextRL = NULL;
struct ListNode * prevRL = NULL;
while (origRL->next != NULL);
{
nextRL = origRL->next;
prevRL = origRL;
origRL = nextRL;
origRL->next = prevRL;
}
}
用于测试它的文件（linkedlist.c）包含在此评论下面。
#include <stdio.h>
#include <stdlib.h>
#include "linkedlist.h"
int main(int argc, char** argv)
{
int i, n;
struct ListNode* head = NULL;
struct ListNode* stack = NULL;
printf("empty list: ");
printList(head);
for(i = 0; i < 23; ++i)
{
n = (i*17+11) % 23;
head = insertSorted(head, n);
stack = pushStack(stack, n);
}
printf("filled list: ");
printList(head);
printf("list length = %d\n", listLength(head));
printf("filled stack: ");
printList(stack);
printf("stack size = %d\n", listLength(stack));
for(i = -4; i < 25; i+=4)
{
n = removeItem(&head, i);
if(!n) printf("remove did not find %d\n", i);
}
printf("list after removes: ");
printList(head);
printf("list length = %d\n", listLength(head));
for(i = 0; i < 5; ++i)
{
printf("pop: %d\n", popStack(&stack));
}
printf("stack after pops: ");
printList(stack);
printf("stack size = %d\n", listLength(stack));
reverseList(&head);
printf("list after reverse: ");
printList(head);
freeList(head);
head = NULL;
freeList(stack);
stack = NULL;
return 0;
}
预期输出
empty list:
filled list: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
list length = 23
filled stack: 17 0 6 12 18 1 7 13 19 2 8 14 20 3 9 15 21 4 10 16 22 5 11
stack size = 23
remove did not find -4
remove did not find 24
list after removes: 1 2 3 5 6 7 9 10 11 13 14 15 17 18 19 21 22
list length = 17
pop: 17
pop: 0
pop: 6
pop: 12
pop: 18
stack after pops: 1 7 13 19 2 8 14 20 3 9 15 21 4 10 16 22 5 11
stack size = 18
list after reverse: 22 21 19 18 17 15 14 13 11 10 9 7 6 5 3 2 1
答案 0 :(得分：0)
您的段错误发生在pushStack()函数中。 *head = *tempPush行在这里毫无意义。当您为NULL传入head指针时，会尝试取消引用它，从而导致段错误。您可以删除此行，并删除不必要的变量dataPush。另外，there is no reason to cast the result of malloc()，最好使用您指定的指针作为sizeof()的参数。如果稍后更改了类型，则避免在sizeof()中使用显式类型意味着要记住更新的内容更少。这意味着新的pushStack()函数是：
struct ListNode * pushStack(struct ListNode *head, int data)
{
struct ListNode *tempPush = malloc(sizeof(*tempPush));
tempPush->data = data;
tempPush->next = head;
return tempPush;
}
您的insertSorted()函数包含错误。我不确定这是哪里;你的功能需要更加复杂，所以我只为你写了一个新功能。同样，您的printList()功能可以简化。我还修改了printList()函数以匹配您提供的预期输出示例：
struct ListNode * insertSorted(struct ListNode *head, int inputData)
{
struct ListNode *prev = NULL;
struct ListNode *curr = head;
struct ListNode *new_node = createNode(inputData);
while (curr) {
if (inputData < curr->data) {
new_node->next = curr;
if (prev)
prev->next = new_node;
return (prev ? head : new_node);
}
prev = curr;
curr = curr->next;
}
if (head) {
new_node->next = NULL;
prev->next = new_node;
} else {
head = new_node;
}
return head;
}
void printList(struct ListNode *head)
{
struct ListNode *curr = head;
while (curr) {
printf("%d ", curr->data);
curr = curr->next;
}
putchar('\n');
}
通过这些更改，输出开始符合您的预期。您的listLength()功能存在问题，popStack()功能存在问题。还可能存在其他问题。我会让你和这些问题搏斗;我的建议应该让你开始。如果您仍有问题，请发送评论，我会尽力帮助您。