编辑：继承更新的插入代码。我会尝试断言，但看看我是否仍然犯了错误
bool SortedList::insert(Student *s){
bool inList = false;
// create an iterator for the list
ListNode *current = head;
// create a new ListNode for the student to be added
ListNode *addition = new ListNode();
// initialize addition to the student and the next to NULL
addition->student = s;
addition->next = NULL;
//while current is not at the end of the list
while(current != NULL){
// if the iteration's ID is equal to the given ID return
// false and delete the ListNode addition
if(current->student->getID() == addition->student->getID()){
delete addition;
return false;
// else if the next student ID in the list is greater than
// the given ID break the while loop
}else if(current->next != NULL && current->next->student->getID() > addition->student->getID()){
inList = true;
break;
}
// otherwise set current to the next student in the list
current = current->next;
}
// if current is at the end of the list and student wasn't found, set
// current next to addition
if(!inList){
current->next = addition;
// else set addition next to current next next and current next to addition
}else{
addition->next = current->next;
current->next = addition;
}
// return true regardless as the student has been added
return true;
}
我在使用这个基本的linkedlist.cpp文件时遇到了一些麻烦。我猜我可能正在使用指针错误或类似的东西。主文件作为目标文件给出，所以我无法查看它，由于某种原因我只想测试插入方法（我睡眠和挣扎极低）。无论如何我在插入方法的某处猜测我引用了NULL错误，但我无法弄清楚在哪里。
错误：分段错误（核心转储） 注意：运行插入
后发生此错误#include <iostream>
#include "SortedList.h"
using namespace std;
/**
* zero argument constructor - initializes an empty list
*/
SortedList::SortedList() : head(NULL){}
/**
* If a student with the same ID is not already in the list, inserts
* the given student into the list in the appropriate place and returns
* true. If there is already a student in the list with the same ID
* then the list is not changed and false is returned.
*
* @param *s a given pointer to a student
* @return boolean value based on whether the student was inserted or not
*/
bool SortedList::insert(Student *s){
// create an iterator for the list
ListNode *current = head;
// create a new ListNode for the student to be added
ListNode *addition = new ListNode();
// initialize addition to the student and the next to NULL
addition->student = s;
addition->next = NULL;
//while current is not at the end of the list
while(current != NULL){
// if the iteration's ID is equal to the given ID return
// false and delete the ListNode addition
if(current->student->getID() == addition->getID()){
return false;
delete addition;
// else if the next student ID in the list is greater than
// the given ID break the while loop
}else if(current->next->student->getID() > addition->getID()){
break;
}
// otherwise set current to the next student in the list
current = current->next;
}
// if current is at the end of the list and student wasn't found, set
// current next to addition
if(current == NULL){
current->next = addition;
// else set addition next to current next next and current next to addition
}else{
addition->next = current->next->next;
current->next = addition;
}
// return true regardless as the student has been added
return true;
}
/**
* Searches the list for a student with the given student ID. If the
* student is found, it is returned; if it is not found, NULL is returned.
*
* @param studentID the given studentID to find in the list
* @return a pointer to a the student found or NULL if the student isn't found
*/
Student * SortedList::find(int studentID){
// create iterator for the list
ListNode *current = head;
// while not at the end of the list iterate
while(current != NULL){
// if the current student ID equals the given student ID return
// the student
if(current->student->getID() == studentID){
return current->student;
}
// otherwise continue iterating
current = current->next;
}
// if not found then return NULL
return NULL;
}
/**
* Searches the list for a student with the given student ID. If the
* student is found, the student is removed from the list and returned;
* if no student is found with the given ID, NULL is returned.
*
* @param studentID the given student ID to be removed from the list
* @return a pointer to the student that was removed or NULL if the student
* wasn't found
*/
Student * SortedList::remove(int studentID){
// create iterator for the list
ListNode *current = head;
// create the to hold the value ahead of the iterator
ListNode *currentNext;
// create to hold the removed student
Student *remove;
// while current is not at the end of the list iterate
while(current != NULL){
// set currentNext to the value ahead of iterator
currentNext = current->next;
// if its ID equals the given ID
if(currentNext->student->getID() == studentID){
// set remove to the student removing
remove = currentNext->student;
// set current next to currentNext next
// (current next next)
current->next = currentNext->next;
//delete the removed ListNode
delete currentNext;
//return the removed student
return remove;
}
}
//if the student wasn't found return NULL
return NULL;
}
/**
* Prints out the list of students to standard output. The students are
* printed in order of student ID (from smallest to largest), one per line
*/
void SortedList::print() const{
//create iterator for list
ListNode *current = head;
//while current is not at the end of the list iterate
while(current != NULL){
// print each individual student and end line
current->student->print();
cout << endl;
//iterate the list
current = current->next;
}
}
答案 0 :(得分：1)
while(current != NULL){
// if the iteration's ID is equal to the given ID return
// false and delete the ListNode addition
if(current->student->getID() == addition->getID()){
2 return false;
delete addition;
// else if the next student ID in the list is greater than
// the given ID break the while loop
1 }else if(current->next->student->getID() > addition->getID()){
break;
}
在我标记为1的行中，您取消引用current->next，而不检查它是否为NULL。此外，在标记为2的行中，您结束exectution，然后然后删除指针。您应delete之前return。
if(current == NULL){
3 current->next = addition;
// else set addition next to current next next and current next to addition
}else{
4 addition->next = current->next->next;
current->next = addition;
}
在标记为3的行中，只有在current时才取消引用NULL。坏juju。在标记为4的行中，您取消引用current->next，而不先检查它是NULL。我想你无论如何都要将addition->next设置为current->next。