普通单向链表应该包含的数据和方法:
结点类(Node):
属性:
AnyType value; //任意类型的数据
Node* next; //指向下一个节点的指针
方法:
构造方法 Node(AnyType* value, Node* next);
链表类(LinkedList):
Node* head; //链表头结点的指针
Node* tail; //链表尾结点的指针,可选
int length; //链表长度,可选
int isEmpty(); //链表是否为空
int contains(); //链表是否包含某个值
void addToHead(AnyType value); //向链表头添加数据
void addToTail(AnyType value); //向链表尾添加数据
void addNode(AnyType value, int index) //向链表指定下标处添加数据
int deleteFromHead(); //从链表头删除一个数据,返回被删除的数据
int deleteFromTail(); //从链表尾删除一个数据,返回被删除的数据
int deleteNode(); //删除指定下标处的数据,返回被删除的数据
实现每种方法的思路:
1、因为LinkedList类的属性有:head,tail,length
所以要根据不同情况更新三个属性
2、所以每种方法,都要处理:
1)head发生变化
2)tail发生变化
的情况
下方是C++代码,有详细注释:
#include<iostream>
#include<string>
#include<stdio.h>
using namespace std;
//节点类,代表链表的结点
class Node{
public:
int value; //存储节点的值
Node* next; //存储下一个节点的指针
Node(int aValue, Node* aNext = NULL){ //构造函数,必须传入结点的值,下一个节点默认为NULL
this->value = aValue;
this->next = aNext;
}
};
class LinkedList{ //普通单向链表类
public:
int length = 0; //链表长度,该属性不重要,下面的方法中也没有用到,但是维护了该属性
Node* head = 0; //链表头节点的指针
Node* tail = 0; //链表尾节点的指针
LinkedList(){
}
int isEmpty(){ //判断链表是否为空,头指针为0代表空
return head == 0;
}
//向链表头添加数据
int addToHead(int aValue){
head = new Node(aValue, head); //添加节点
if (tail == 0) tail = head; //如果尾指针为空,说明链表本身为空,更新尾指针
length++;
}
//向链表尾添加数据
int addToTail(int aValue){
//如果尾指针为空,说明链表本身为空,更新尾指针和头指针
if (tail == 0) head = tail = new Node(aValue);
//否则只更新尾指针
else tail = tail->next = new Node(aValue);
length++;
}
//从链表头删除数据
int deleteFromHead(){
//如果链表为空,无法删除,返回-1
if (head == 0) return -1;
//记录被删除的结点指针和值
Node* deletedNode = head;
int deletedValue = head->value;
if (head == tail) //如果链表只有一个结点,那么删除后头和尾都为空
head = tail = 0;
else
head = head->next;
length--;
delete deletedNode;
return deletedValue; //返回被删除的值
}
int deleteFromTail(){
//如果链表为空,无法删除,返回-1
if (head == 0) return -1;
//记录被删除的结点指针和值
Node* deletedNode = tail;
int deletedValue = tail->value;
if (head == tail) //如果链表只有一个结点,那么删除后头和尾都为空
head = tail = 0;
else {
Node* now = 0;
for(now=head; now->next!=tail; now=now->next); //遍历链表,找到倒数第二个结点
//printf("Fine -2 Node Value: %d\n", now->value);
now->next = 0;
tail = now;
}
length--;
delete deletedNode;
return deletedValue; //返回被删除的值
}
int deleteNode(int index){
if (index <= 0) return -1;
//如果链表为空,无法删除,返回-1
if (head == 0) return -1;
Node* now = 0;
int cnt = 1; //计数器
/*
下面的循环作用:
情况1:正常情况下,找到要删除的结点的前一个结点;
情况2:如果要删除的结点序号大于总结点数,使得找到的值停止在NULL
*/
for(now=head; cnt+1<index && now!=0; cnt++,now=now->next);
//printf("Find now: value: %d\n", now->value);
if(now == 0) return -1; //情况2发生,直接返回
//记录被删除的结点指针和值
Node* deletedNode = now->next;
int deletedValue = deletedNode->value;
//情况1:将该结点删除
if (cnt == index-1)
now->next = now->next->next;
length--;
//如果末尾结点被删除,更新tail
if (deletedNode->next == 0){
tail = now;
}
delete deletedNode;
return deletedValue;
}
//向指定序号处插入结点
void addNode(int value, int index){ //index starts from 1
if (index <= 0) return;
//处理链表为空插入结点的情况
if (head == 0 && index == 1) {
head = tail = new Node(value);
length++;
return ;
}
//处理在链表头插入数据的情况
if (index == 1){
head = new Node(value, head);
length++;
return ;
}
Node* aheadOfAdd = NULL;
int cnt = 1;
//循环找到要插入的结点之前的那个结点
for (aheadOfAdd=head,cnt=1; aheadOfAdd!=0&&cnt+1<index; cnt++,aheadOfAdd=aheadOfAdd->next);
//如果以上循环因为条件“cnt+1<index”不成立而终止,则因为要插入的结点序号超过了链表总大小
if (!index == cnt+1)
return ;
if (aheadOfAdd == 0)
return ;
//printf("%d\n", aheadOfAdd->value);
aheadOfAdd->next = new Node(value, aheadOfAdd->next);
length++;
//如果向尾部插入了结点,更新tail
if (aheadOfAdd->next->next == 0) tail = aheadOfAdd->next;
}
void printSelf(){ //打印链表内容
Node* nodeToPrint = this->head;
printf("Content of LinkedList:");
while(nodeToPrint != NULL){
printf("%d ", nodeToPrint->value);
if(nodeToPrint == tail)
printf("tail is reached!\n");
nodeToPrint = nodeToPrint->next;
}
printf("\n");
}
//判断链表是否包含某个值
bool contains(int value){
for(Node* now=head; now!=0; now=now->next)
if (now->value == value)
return true;
return false;
}
};
//测试程序
int main(){
LinkedList* list = new LinkedList();printf(" %d\n", list->length);
list->addToHead(1);list->printSelf();printf(" %d\n", list->length);
list->addToHead(2);list->printSelf();printf(" %d\n", list->length);
list->addToHead(3);list->printSelf();printf(" %d\n", list->length);
list->addToHead(4);list->printSelf();printf(" %d\n", list->length);
list->addToTail(100);list->printSelf();printf(" %d\n", list->length);
list->addToTail(101);list->printSelf();printf(" %d\n", list->length);
list->addToTail(102);list->printSelf();printf(" %d\n", list->length);
list->addToTail(103);list->printSelf();printf(" %d\n", list->length);
list->deleteNode(8);list->printSelf();printf(" %d\n", list->length);
printf("%d",list->contains(103));
}