C++实现单链表(Singly-Linked List)追加、遍历、删除

<pre name="code" class="cpp">#include <iostream>
using namespace std;

struct Node
{
int data;
struct Node* next;
};

class List
{
Node* head;
public:
List() { head = NULL;}
void Print();
int GetSize();
void Append(int addData);
void EraseOne(int eraseData);
void EraseOne_V2(int eraseData);
};

void List::Print()
{
Node* tmp = head;

//list is empty
if (tmp == NULL)
{
cout << "Empty List!\n";
return;
}

//list is not empty
for(; tmp != NULL; tmp = tmp->next)
{
cout << tmp->data << " --> ";
}
cout << "NULL\n";
}

int List::GetSize()
{
Node* tmp = head;

//list is empty
if(tmp == NULL)
{
return 0;
}

//list is not empty
int num(0);
for(; tmp != NULL; tmp = tmp->next)
{
++num;
}
return num;
}

void List::Append(int addData)
{
//create a new node
Node* newNode = new Node;
newNode->data = addData;
newNode->next = NULL;

Node* tmp = head;

//list is empty
if(tmp == NULL)
{
head = newNode; //有可能引入重复释放指针的问题，可以使用智能指针。
return;
}

//list is not empty, locate the last node
for(; tmp->next != NULL; tmp = tmp->next)
{
}

tmp->next = newNode;

}

void List::EraseOne_V2(int eraseData)
{
Node* tmp = head;

//空链表
if (tmp == NULL)
{
return;
}

//只有一个节点的链表
if (tmp->next == NULL)
{
if (tmp->data == eraseData)
{
delete tmp;
head = NULL;
}
return;
}

//有两个及以上节点的链表，待删节点正是首节点
if (tmp->data == eraseData)
{
head = head->next;
delete tmp;
tmp = NULL;
}

//有两个及以上节点的链表，待删节点不是首节点
for (; tmp != NULL; tmp = tmp->next)
{
if ((tmp->next != NULL)  &&  (tmp->next->data == eraseData)) //找到待删节点的前一个节点
{
Node* tmp2 = tmp->next;
tmp->next = tmp->next->next;
delete tmp2;
break;
}
}
}

void List::EraseOne(int eraseData)
{
Node* tmp = head;

////////////////////
//list is empty
////////////////////
if(tmp == NULL)
{
return;
}

////////////////////
//list is not empty
////////////////////
int locate(-1), idx(0);
for(; tmp != NULL; tmp = tmp->next)
{
++idx;
if(tmp->data == eraseData)
{
locate = idx - 1;
break;
}
}

if(locate == -1) // eraseData not found
{
return;
}

int listSize = GetSize();

if(listSize == 1) // only one node in the list
{
delete head;
head = NULL;
}
else // more than one node in the list
{
// eraseData is the 0th node
if(locate == 0)
{
tmp = head;
head = head->next;
delete tmp; //注意这里释放tmp（并没有用new申请空间给tmp)的空间是可行的，我的理解是因为tmp是结构体指针（相对于基本数据类型指针）。但是不能重复释放。
tmp = NULL;
}

//eraseNode is the last node
if(locate == listSize - 1)
{
tmp = head;
int idx(0);
for(; tmp != NULL; tmp = tmp->next)
{
++idx;
if(idx == locate - 1)
{
Node* toDel = tmp->next;
tmp->next = NULL;
delete toDel;
}
}
}

// eraseData is intermediate node
if(locate > 0  &&  locate < listSize - 1)
{
tmp = head;
int idx(0);
for(; tmp != NULL; tmp = tmp->next)
{
++idx;
if(idx == locate - 1)
{
Node* toDel = tmp->next;
tmp->next = tmp->next->next;
delete toDel;
}
}
}
} // more than one node in the list
}

int main (int argc, char** argv)
{
// New list
List list;
list.Print();

list.EraseOne_V2(100);

list.Append(2);
list.Print();
list.EraseOne_V2(2);
list.Print();

// Append nodes to the list
list.Append(100);
list.Print();
list.Append(200);
list.Print();
list.Append(300);
list.Print();
list.Append(300);
list.Print();
list.Append(500);
list.Print();

// Delete nodes from the list
list.EraseOne_V2(400);
list.Print();
list.EraseOne_V2(100);
list.Print();
list.EraseOne_V2(200);
list.Print();
list.EraseOne_V2(500);
list.Print();
list.EraseOne_V2(100);
list.Print();
list.EraseOne_V2(300);
list.Print();

return 0;
}

100 --> NULL
100 --> 200 --> NULL
100 --> 200 --> 300 --> NULL
100 --> 200 --> 300 --> 300 --> NULL
100 --> 200 --> 300 --> 300 --> 500 --> NULL
100 --> 200 --> 300 --> 300 --> 500 --> NULL
100 --> 300 --> 300 --> 500 --> NULL
100 --> 300 --> 300 --> 500 --> NULL
100 --> 300 --> NULL
300 --> NULL
Empty List!