Reputation: 95
i create a simple Linked list use class.in my class,i have 3 method are:push_back()
,push_front()
,and print() to print list.I have some problem with pointer p in push_front()
. When debug by vs 2013,value
and next
of p is "unable to read memory",and i can't understand that,so pls explain for me.
#include <stdio.h>
#include <iostream>
using namespace std;
class Note
{
public :
int value;
Note *next;
public :
Note(int value)
{
this->value = value;
this->next = NULL;
}
Note(int value,Note *next)
{
this->value = value;
this->next = next;
}
};
class LinkList
{
public :
Note *head;
public :
LinkList()
{
head = NULL;
}
void Push_back(int value)
{
Note *p = NULL;
if (head == NULL)
{
head = new Note(value, NULL);
}
else
{
p = head;
while (p->next != NULL)
p = p->next;
p->next = new Note(value, NULL);
}
}
void Push_front(int value)
{
Note *p = NULL;
p->value = 3;
p->next = this->head;
}
void print()
{
Note *p = NULL;
p = head;
while (p != NULL)
{
cout << p->value<<endl;
p = p->next;
}
}
int main()
{
LinkList test;
test.Push_back(6);
test.Push_back(5);
test.Push_back(12);
test.Push_front(13);
test.print();
}
Upvotes: 3
Views: 193
Reputation: 300837
You have not allocated any memory for p to point at:
void Push_front(int value)
{
Note *p = NULL;
^^^^^^^^
// you are missing an allocation of a Note object:
// p = new Note;
p->value = 3;
p->next = this->head;
}
Upvotes: 4