我在C ++做一个程序来删除单链接列表中的节点，但因为预测它无法正常工作。我附上输出的画面，更清晰，即什么行为不端。码：
int del_node(int val_del) //this section is producing error
{
node* temp_del=head;
if(head==nullptr)
{
cout<<"no element to delete.!";
exit(0);
}
else
{
while(temp_del->next!=nullptr)
{
if(temp_del->next->data==val_del)
{
temp_del->next=temp_del->next->next;
delete temp_del->next->next;
}
temp_del=temp_del->next;
}
}
return 0;
}
这是一个一类的功能。下面是完整的代码，如果有帮助：
#include<iostream>
using namespace std;
struct node
{
int data;
node *next;
};
class linked_list
{
node *head,*tail;
public:
linked_list()
{
head=nullptr;
tail=nullptr;
}
int create_last(int val_last)
{
node *temp=new node; if(!temp){cout<<"memory not allocated"; exit(1);}
temp->data=val_last;
temp->next=nullptr;
if(head==nullptr)
{
head=temp;
tail=temp;
}
else
{
tail->next=temp;
tail=temp;
}
return 0;
}
int create_beg(int val_beg)
{
node *temp_head=nullptr;
node *temp=new node; if(!temp){cout<<"memory not allocated"; exit(1);}
temp->data=val_beg;
temp->next=nullptr;
if(head==nullptr)
{
head=temp;
tail=temp;
}
else
{
temp_head=head;
head=temp;
temp->next=temp_head;
}
return 0;
}
int del_node(int val_del) //this section is producing error
{
node* temp_del=head;
if(head==nullptr)
{
cout<<"no element to delete.!";
exit(0);
}
else
{
while(temp_del->next!=nullptr)
{
if(temp_del->next->data==val_del)
{
temp_del->next=temp_del->next->next;
delete temp_del->next->next;
}
temp_del=temp_del->next;
}
}
return 0;
}
int show()
{
node* temp_show=head;
while(temp_show!=nullptr)
{
cout<<temp_show->data<<"\n";
temp_show=temp_show->next;
}
return 0;
}
}info;
int main()
{
int choice,ele; char cont;
rep:
cout<<"1. Insert node at the end\n";
cout<<"2. Insert node at beg\n";
cout<<"3. Delete node\n";
cout<<"4. Show nodes\n";
cout<<"5. Exit\n";
cout<<"enter your choice: ";
cin>>choice;
switch(choice)
{
case 1: cout<<"Enter element: ";
cin>>ele;
info.create_last(ele);
break;
case 2: cout<<"Enter element: ";
cin>>ele;
info.create_beg(ele);
break;
case 3: cout<<"Enter element: ";
cin>>ele;
info.del_node(ele);
break;
case 4: info.show();
break;
case 5: exit(0);
break;
default: cout<<"Wrong choice, Bye.!!";
exit(0);
}
cout<<"Do you want to continue(y/n): ";
cin>>cont;
if(cont=='y'||cont=='Y')
{
goto rep;
}
else
{
cout<<"thank you";
exit(0);
}
return 0;
}
int del_node(int val_del) {
node* temp_del = head;
if(head == nullptr) {
cout<<"no element to delete.!";
exit(0);
} else if(head->data == val_del) {
// If head is to be deleted
head = head->next;
} else {
while(temp_del->next != nullptr) {
if(temp_del->next->data == val_del) {
temp_del->next=temp_del->next->next;
// delete temp_del->next->next; This is wrong deletion
}
temp_del = temp_del->next;
}
}
// delete the node if one found else not
if (temp_del != nullptr)
delete temp_del;
return 0; // This should return true or false, do check what you want as return type
}
该del_node功能有两个问题：
1）它不能删除节点时列表中恰好有1元
2）删除错误的元素
因此，让我们开始与1号和看代码：
if(head==nullptr)
{
cout<<"no element to delete.!";
exit(0);
}
else
{
while(temp_del->next!=nullptr)
假设该列表包含一个元素。这意味着：
一）head不是NULL
B）head->next并且因此也temp_del->next是NULL
所以while(temp_del->next!=nullptr)将导致虚假的，即循环将不被执行。总的结果是，代码什么也不做。
现在的号码2的代码是：
if(temp_del->next->data==val_del)
{
temp_del->next=temp_del->next->next; // You want to delete temp_del->next
// but here you change it
delete temp_del->next->next; // so here you delete the wrong node
// there is also an extra ->next
}
你需要一个临时变量的指针坚持要删除的节点。
你可能想要的代码是：
int del_node(int val_del)
{
// Delete elements in the front
while (head!=nullptr && head->data==val_del)
{
node* node_to_delete = head;
head = head->next;
delete node_to_delete;
// return 0; Uncomment if you only want one delete per function call
}
if(head==nullptr) return 0;
// Delete elements not in the front
node* temp_del=head;
while(temp_del->next!=nullptr)
{
if (temp_del->next->data==val_del)
{
node* node_to_delete = temp_del->next;
temp_del->next = temp_del->next->next;
delete node_to_delete;
// return 0; Uncomment if you only want one delete per function call
}
temp_del=temp_del->next;
}
return 0;
}