我试图在c ++中将值存储在链表中并打印它们。但我不知道我是否正在编写正确的代码。当我创建一个新的节点插入值 - 打印时，这可行。但是当我在最后使用temp打印所有值时都不起作用
grok {
match => {"metadata"=> "%{GREEDYDATA:first_name}_%{GREEDYDATA:last_name}_%{TIMESTAMP_ISO8601:time}"}
}
显示的输出 #include <iostream>
using namespace std;
struct node
{
int val;
node *next;
};
int main()
{
node *temp = new node(); //creating the first node
node *head, *tail;
temp->val= 1; //assigning value to the first node
head = temp; //head contains the address of 1st node
cout<< "head value" <<head << endl;
cout << "head value" << temp << endl;
cout<< "1st value" << temp->val << endl;
cout << "=================================================" << endl;
//============================================second node
temp = temp->next;
temp = new node();
temp->val = 2;
cout << "head value" << head << endl;
cout << "head value" << temp << endl;
cout << "2rd value" << temp->val << endl;
cout << "=================================================" << endl;
//============================================third node
temp = temp->next;
temp = new node();
temp->val = 3;
cout << "head value" << head << endl;
cout << "head value" << temp << endl;
cout << "3rd value" << temp->val << endl;
tail = temp;
temp->next = NULL;
cout<< "=================================================" << endl;
cout<< "value in head" << head->val << endl;
cout << "=================================================" << endl;
cout<< "the value temp is reset to head which is the location of first node" << endl;
cout << "=================================================" << endl;
//temp = NULL;
temp = head; //add of first node is stored in temp
cout<< "the value of head " << head << endl;
cout<< "the value of temp " << temp << endl;
//Problem from this ............................................................
//temp->next = head->next;
cout << "the value of head " << head->next << endl;
cout << "the value of temp " << temp->next << endl;
cout<< "value in head + 1 " << temp->val << endl;
system("pause");
return 0;
}
的地址不起作用
output photo
答案 0 :(得分：1)
声明
temp = temp->next;
使temp指向与temp->next指向的内存相同的内存。这是一个空指针。
然后
temp = new node();
覆盖temp的上一个值，并使其指向新分配的node结构。
以上两个语句没有将新节点链接到列表中。
而是尝试像
这样的东西// At this point `temp` is pointing to the last node in the list
// Create a new node and link it into the list
temp->next = new node; // Allocate a new `node` and link it into the list
temp = temp->next; // Make `temp` point to the new node
temp->val = ...; // Set the new value
...
答案 1 :(得分：0)
temp是一个单独的变量，它占用一个单独的内存范围。
所以在这些陈述之后
temp = temp->next;
temp = new node();
更改了变量temp。但是先前指向的节点的数据成员temp->next没有被更改，因为temp->next占用了不同的内存范围。
结果您没有链接列表。您有单独的节点未链接。
您可以使用temp类型的变量node **以下列方式实现您想要的效果。
#include <iostream>
#include <cstdlib>
using namespace std;
struct node
{
int val;
node *next;
};
int main()
{
node *head, *tail;
node **temp = &head;
*temp = new node(); //creating the first node
( *temp )->val= 1; //assigning value to the first node
cout<< "head value" <<head << endl;
cout << "head value" << *temp << endl;
cout<< "1st value" << ( *temp )->val << endl;
cout << "=================================================" << endl;
//============================================second node
temp = &( *temp )->next;
*temp = new node();
( *temp )->val = 2;
cout << "head value" << head << endl;
cout << "head value" << *temp << endl;
cout << "2rd value" << ( *temp )->val << endl;
cout << "=================================================" << endl;
//============================================third node
temp = &( *temp )->next;
*temp = new node();
( *temp )->val = 3;
cout << "head value" << head << endl;
cout << "head value" << *temp << endl;
cout << "3rd value" << ( *temp )->val << endl;
tail = *temp;
( *temp )->next = NULL;
cout<< "=================================================" << endl;
cout<< "value in head" << head->val << endl;
cout << "=================================================" << endl;
cout<< "the value temp is reset to head which is the location of first node" << endl;
cout << "=================================================" << endl;
//temp = NULL;
temp = &head; //add of first node is stored in temp
cout<< "the value of head " << head << endl;
cout<< "the value of temp " << *temp << endl;
//Problem from this ............................................................
//temp->next = head->next;
cout << "the value of head " << head->next << endl;
cout << "the value of temp " << ( *temp )->next << endl;
cout<< "value in head + 1 " << ( *temp )->next->val << endl;
system("pause");
return 0;
}
程序输出可能看起来像
head value0x55ab880e8c20
head value0x55ab880e8c20
1st value1
=================================================
head value0x55ab880e8c20
head value0x55ab880e9c50
2rd value2
=================================================
head value0x55ab880e8c20
head value0x55ab880e9c70
3rd value3
=================================================
value in head1
=================================================
the value temp is reset to head which is the location of first node
=================================================
the value of head 0x55ab880e8c20
the value of temp 0x55ab880e8c20
the value of head 0x55ab880e9c50
the value of temp 0x55ab880e9c50
value in head + 1 2
答案 2 :(得分：0)
这有效..
#include <iostream>
using namespace std;
struct node
{
int val;
node *next;
};
int main()
{
node *temp, *head, *tail;
temp = new node(); //creation of first node structure
temp->val = 1; //value of 1st node
head = temp; //assigning the temp address to head
cout<< "the add of head "<<head << endl;
cout<< "the add of temp "<< temp << endl;
cout<< "the value in 1st node is "<< temp->val << endl;
cout<< "=================================================" << endl;
temp->next = new node(); //creation of second node structure
temp = temp->next; //over writing the first address of temp with the
//address of second node
temp->val = 2;
cout << "the add of head " << head << endl;
cout << "the add of temp " << temp << endl;
cout << "the value in 2nd node is " << temp->val << endl;
cout << "=================================================" << endl;
temp->next = new node(); //creation of third node structure
temp = temp->next; //over writing the second address of temp with the
//address of third node
temp->val = 3;
cout << "the add of head " << head << endl;
cout << "the add of temp " << temp << endl;
cout << "the value in 3nd node is " << temp->val << endl;
cout << "=================================================" << endl;
temp->next = NULL; //the last node pointer pointers to null
temp = head; //temp is assigned the value of head which is
//the address of 1st node
cout << "the add of head " << head << endl;
cout << "the add of temp " << temp << endl;
cout << "the value in 1st node is " << temp->val << endl;
cout << "=================================================" << endl;
temp = temp->next; //the address of second node is assigned to temp
cout << "the add of head " << head << endl;
cout << "the add of temp " << temp << endl;
cout << "the value in 2nd node is " << temp->val << endl;
cout << "=================================================" << endl;
temp = temp->next; //the address of third node is assigned to temp
cout << "the add of head " << head << endl;
cout << "the add of temp " << temp << endl;
cout << "the value in 3nd node is " << temp->val << endl;
cout << "=================================================" << endl;
system("pause");
return 0;
}