我的任务是实现一个带有链表的集合。我很快创建了链表，然后开始构建集。我在设置操作（联合/交集/差异）上有点挣扎但是在实现之后我试图制作一个驱动程序方法，现在我得到了包含/添加的段错误。我无法正确检查我的操作结果。我不明白为什么我会收到这个错误。我忽略了什么...任何帮助将不胜感激。
Linklist.h
class ListNode
{
private:
ListNode* prev;
ListNode* next;
int data;
public:
ListNode() { prev = next = NULL;
data=0;}
ListNode(int d, ListNode* p, ListNode* n) { data = d; prev = p; next = n; }
friend class List;
};
class List
{
private:
ListNode* head;
ListNode* tail;
public:
List() { head = tail = NULL; }
~List();
bool isEmpty() { return head == NULL; }
bool contains(int value);
void addToHead(int value);
void addToTail(int value);
int removeHead();
int removeTail();
int removeAt(int index);
bool remove(int value);
int at(int index);
int valueOf(const ListNode* elem);
const ListNode* getNext(const ListNode* node);
const ListNode* getPrevious(const ListNode* node);
const ListNode* getHead() { return head; }
const ListNode* getTail() { return tail; }
void print();
};
List::~List()
{
while (!isEmpty())
removeTail();
}
bool List::contains(int value)
{
ListNode *tmp = head; // <**This is where error occurs**
while (tmp != NULL && tmp->data != value)
tmp = tmp->next;
return tmp != NULL;
}
void List::addToHead(int value)
{
if (isEmpty())
{
head = tail = new ListNode(value, NULL, NULL);
}
else
{
head = new ListNode(value, NULL, head);
head->next->prev = head;
}
}
void List::addToTail(int value)
{
if (isEmpty())
{
head = tail = new ListNode(value, NULL, NULL);
}
else
{
tail = new ListNode(value, tail, NULL);
tail->prev->next = tail;
}
}
int List::removeHead()
{
int value = head->data;
if (head == tail)
{
delete tail;
head = tail = NULL;
}
else
{
head = head->next;
delete head->prev;
head->prev = NULL;
}
return value;
}
int List::removeTail()
{
int value = head->data;
if (head == tail)
{
delete tail;
head = tail = NULL;
}
else
{
tail = tail->prev;
delete tail->next;
tail->next = NULL;
}
return value;
}
int List::removeAt(int index)
{
// Remove the node at index. Return the int value contained at
// the now removed node. Exit program if an invalid
ListNode *temp = head;
int i=0;
if (index == 0) {
removeHead();
}
while (temp != NULL && i < index-1) {
temp = temp->next;
i++;
}
if (temp == NULL || temp -> next == NULL ) {
exit(1);
}
else{
ListNode* temp2 = temp->next;
temp->next = temp->next->next;
temp2->next = NULL;
delete temp2; }
}
bool List::remove(int value)
{
// Remove the provided value if it is contained in the list. Return true if the
// value was found and remove, return false if no changes were made to the list
ListNode *prev = head;
ListNode* temp = head->next;
if (prev->data==value){
removeHead();
}
else {
while (temp != NULL && temp->data != value) {
prev = temp;
temp = temp->next;
}
if (temp == NULL) {
cout << "No change" << endl;
return false;
} else {
prev->next = temp->next; // unlink the node you remove
delete temp; // delete the node
}
}
}
int List::at(int index)
{
// Returns the int value contained at the node at the provided index. Exit program if
// an invalid index is provided
ListNode *temp = head;
for(int i=1; i < index; i++) {
if (temp -> next == NULL){
exit(1);
}
temp = temp->next;
}
return valueOf(temp);
}
int List::valueOf(const ListNode* elem)
{
return elem->data;
}
const ListNode* List::getNext(const ListNode* node)
{
return node->next;
}
const ListNode* List::getPrevious(const ListNode* node)
{
return node->prev;
}
void List::print() {
ListNode *tmp = head;
if (tmp != NULL) {
do {
if (tmp != NULL) {
cout << tmp->data << " -> ";
tmp = tmp->next;
}
} while (tmp != NULL);
}
cout << endl;
}
#endif //UNTITLED4_LIST_H
集
#include <iostream>
#include "list.h"
using namespace std;
class Set
{
private:
List* list;
int set_size;
public:
Set();
~Set();
bool contains(int value);
bool add(int value);
bool remove(int value);
void clear();
Set* set_union(Set&);
Set* intersection(Set&);
Set* difference(Set&);
void print();
int size() { return set_size; }
};
Set::Set() {
list = NULL;
set_size = 0;
}
Set::~Set() {
delete list;
set_size = 0;
}
bool Set::contains(int value) {
// Returns a boolean value representing if the provided int value is contained
//in the list
if(list->contains(value)){
return false;
}
else{
list->addToHead(value);
set_size++;
return true;
}
}
bool Set::add(int value) {
// Returns a boolean value representing if the provided int value was successfully
// added to the list do not allow duplicate
if (!contains(value))
{ list->addToTail(value);}
else {return false;}
}
bool Set::remove(int value) {
return list->remove(value);
}
void Set::clear() {
//This function should assign 0 to set_size, and delete list.
set_size = 0;
delete list;
}
Set *Set::set_union(Set &s) {
//Creates and returns a Set pointer that contains the set union of the
//invoking Set object and a second Set object passed into the function
Set *temp = new Set();
for(int t= 1;t<s.set_size; t++)
temp->add(s.list->at(t));
return temp;
}
Set *Set::intersection(Set &s) {
// Creates and returns a Set pointer that contains the set intersection of the
// invoking Set object and a second Set object passed into the function.
Set *temp = new Set();
for ( int i = 0; i < set_size; i++) {
if (s.contains(list->at(i))) {
temp->add(list->at(i));
}
}
return temp;
}
Set *Set::difference(Set &s) {
// Creates and returns a Set pointer that contains the set difference between
// the invoking Set object and a second Set object passed into the function. The
// invoking Set object should be considered the set that is being subtracted from (
// Invoking Set – Parameter Set)
Set *temp = new Set();
for ( int i = 0; i < set_size; i++) {
if (s.contains(list->at(i))) {
temp->add(list->at(i));
}
}
for( int i = 0; i < set_size; i++){
if (temp->contains(list->at(i))) {
s.remove(list->at(i));
}
}
return temp;
}
void Set::print() {
// TO DO --- Already have print in list
}
int main() {
int choice, item, size1, size2;
cout << "Please Enter the starting Value of Set#1:";
cin >> size1;
Set set1;
cout << "\nPlease Enter the starting Value of Set#2:";
cin >> size2;
Set set2;
cout << "\n Enter " << size2 << " numbers in Set1:";
for (int i = 1; i < size1; i++) {
cin >> item;
set1.add(item);
}
cout << "\n Enter " << size2 << " numbers in Set2:";
for (int i = 1; i < size1; i++) {
cin >> item;
set2.add(item);
}
while (choice !=7) {
cout << "1.Insert Element into the Set" << endl;
cout << "2.Delete Element of the Set" << endl;
cout << "3.Size of the Set" << endl;
cout << "4.Union of Set" << endl;
cout << "5.intersections of set" << endl;
cout << "6.difference of set" << endl;
cout << "7.Exit" << endl;
cout << "Enter your Choice: ";
cin >> choice;
switch (choice) {
case 1:
cout << "Enter value to be inserted: ";
cin >> item;
// st.insert(item);
break;
case 2:
cout << "Enter the element to be deleted: ";
cin >> item;
//st.erase(item);
break;
case 3:
cout << "Size of the Set1: ";
cout << set1.size() << endl;
cout << "\nSize of the Set2: ";
cout << set2.size() << endl;
break;
case 4:
break;
case 5:
break;
case 6:
exit(1);
default:
cout << "Wrong Choice" << endl;
}
}
return 0;
}
答案 0 :(得分：0)
您的Set对象包含指向List（链接列表）的指针，该指针已分配给NULL构造函数中的Set，但此List没有内存永远分配。这就是为什么每次尝试对List进行操作时，您的应用程序会出现段错误。
您需要：
Set保持List而不是List*）List对象中保存的new（ Set ）正确分配内存。