一个小程序 为什么不能运行啊？
#include <iostream.h>
#include <stdio.h>
class ListNode
{
friend class List;
double value;
ListNode * next;
};
class List
{
int nCount;
ListNode * head;
public:
List() //无参构造函数
{nCount=0;
head->next=NULL;
}
/* List(List &l) //拷贝构造函数
{int i;
for(i=l.nCount;i>=0;i--)
List->value=l->value;
}*/
~List() //析构函数
{
delete head;
}
List & operator = (List & l) //重载等号运算符
{ nCount=l.nCount;
head=l.head;
return *this;
}
void Add(double d) //添加一个元素
{ ListNode *p,*q;
p=new ListNode;
q=head;
while(q->next!=NULL)
{q=q->next;
}
q->next=p;
p->value=d;
nCount++;
}
void Remove(double d) //删除一个元素
{ListNode *p=head->next;
ListNode *s=head;
while(p->value!=d)
{p=p->next;
s++;
}
s->next=p->next;
delete(p);
nCount--;
}
void Print()
{
if( head==NULL) return;
cout << "LIST(" << nCount <<") =" << head->value;
ListNode * p=head->next;
while(p!=NULL)
{
cout << ", "<< p->value;
p=p->next;
}
cout <<endl;
}
};
void main()
{
List list1;
double d;
int n;
cin >>n;
while (n>0)
{
cin >>d;
list1.Add(d);
n--;
}
list1.Print();
List list2;
list2.Add(2.4);
list2.Add(6.1);
list2.Print();
list2=list1;
cin >>d;
list2.Remove(d);
cin >>d;
list2.Remove(d);
list2.Print();
}
[解决办法]
无参构造函数 List() 里 head->next=NULL;会出错，因为head未指向一个结构体实例，应该先
head=new ListNode();head->next=NULL;这也许只是其中一个错误，，其它的自己再找找
[解决办法]
- C/C++ code
#include <iostream>using namespace std;#include <stdio.h>class ListNode{ friend class List; double value; ListNode * next;};class List{ int nCount; ListNode * head;public: List() //无参构造函数 { nCount=0; head=NULL; } ~List() //析构函数 { ListNode* p = head,*q; while(p) { q = p->next; delete p; p = q; } } List & operator = (List & l) //重载等号运算符 { nCount=l.nCount; head=l.head; return *this; } void Add(double d) //添加一个元素 { if (head == NULL) { head = new ListNode; head->value = d; head->next = NULL; return; } ListNode *p,*q; p=new ListNode; p->next = NULL; q=head; while(q->next!=NULL) { q=q->next; } q->next=p; p->value=d; nCount++; } void Remove(double d) //删除一个元素 { ListNode *p; if(head->value==d) { p = head; head = head->next; delete p; return; } p=head->next; ListNode *s=head; while(p->value!=d) { p=p->next; s=s->next; } s->next=p->next; delete(p); nCount--; } void Print() { if( head==NULL) return; cout << "LIST(" << nCount <<") =" << head->value; ListNode * p=head->next; while(p!=NULL) { cout << ", "<< p->value; p=p->next; } cout <<endl; }};void main(){ List list1; double d; int n; cin >>n; while (n>0) { cin >>d; list1.Add(d); n--; } list1.Print(); List list2; list2.Add(2.4); list2.Add(6.1); list2.Print(); list2=list1; cin >>d; list2.Remove(d); cin >>d; list2.Remove(d); list2.Print();}
[解决办法]
- C/C++ code
#include <iostream.h>#include <stdio.h>class ListNode{ friend class List; double value; ListNode * next;};class List{ int nCount; ListNode * head;public: List() //无参构造函数 { nCount=0; head = new ListNode;//<----------------------------------here head->next=NULL; } /* List(List &l) //拷贝构造函数 {int i;for(i=l.nCount;i>=0;i--)List->value=l->value; }*/~List() //析构函数{ RemoveAll();}void RemoveAll()//<-----------------------------增加一个函数{ ListNode *temp = NULL; while (head!=NULL) { temp=head; head=head->next; delete temp; }}List & operator = (List & l) //重载等号运算符{ ListNode *p, *s; if (&l != this) { nCount=l.nCount; this->RemoveAll(); } head=new ListNode; head->next=NULL; p=head; s=l.head; while (s->next) { s=s->next; p->next=new ListNode; p->next->value=s->value; p=p->next; } p->next=NULL; return *this;}void Add(double d) //添加一个元素{ ListNode *p,*q; p=new ListNode; q=head; while(q->next!=NULL) { q=q->next; } q->next=p; p->value=d; p->next=NULL;//<---------------------------------------------------here nCount++;} void Remove(double d) //删除一个元素{ ListNode *p=head->next; ListNode *s=head; while(p->value!=d) { p=p->next; s=s->next;//<----------------------------here } s->next=p->next; delete(p); nCount--; }void Print(){ if( head==NULL) return; cout << "LIST(" << nCount <<") =";//<-----------------------------here ListNode * p=head->next; while(p->next!=NULL)// here { cout << p->value<<", "; p=p->next; } cout<<p->value;//<--------------------------------here cout <<endl; }};void main(){ List list1; double d; int n; cin >>n; while (n>0) { cin >>d; list1.Add(d); n--; } list1.Print(); List list2; list2.Add(2.4); list2.Add(6.1); list2.Print(); list2=list1; list2.Print();//<-------------------here cin >>d; list2.Remove(d); cin >>d; list2.Remove(d); list2.Print();}
[解决办法]
list2=list1;//你把1给2，那2原来的所有节点不就全丢了？为什么要这样做？
此外，声明一个新的对象list2，当赋给它链表时，两个指针指向了同一链表，当运行结束，调用析构函数释放内存时就会出现释放"悬挂指针"的内存错误
operator=重载问题，用智能指针吧
[解决办法]
改动了你的函数
- C/C++ code
void Remove(double d) //删除一个元素 { ListNode *p = head, *q = head; if (head == NULL)//表空退出 { return; } while (p && p->value != d)//寻寻觅觅 { q = p; p=p->next; } if (p == NULL)//众里寻他千百度，蓦然回首TMD的没有 { return; } //找到了，那就让它滚蛋，而且快快的 if (q == head)//第一个结点——这里头结点你存数据了，只能特殊时期，特殊对待 { head = head ->next; delete q; nCount--; } else { q->next = p->next; delete(p); nCount--; } }