1 问题

用C++语言实现链表

 

 

 

 

 

2 代码实现

#include <iostream>
#include <stdlib.h>using namespace std;class List
{
public:List();~List();List* createNode(int value);//创建节点bool insertNode(List *node);//插入节点void printList();//打印节点bool deleteNode(List *node);//删除节点不移动头节点bool deleteNode1(List *node);//删除节点移动头节点int listSize();//长度void printNode();//打印但前的valuevoid freeList();//释放链表
private:int value;List *head;List *next;
};bool List::deleteNode(List *node)
{if (node == NULL){std:cout << "node is NULL" << std::endl;	return false;}if (head == NULL){std::cout << "head is NULL" << std::endl;	return false;}//如果node等于headif (head == node){head = head->next;}List *p = head;while (p->next != NULL){if (p->next == node){p->next = p->next->next;return true;}p = p->next;}return false;	
}bool List::deleteNode1(List *node)
{if (node == NULL){std:cout << "node is NULL" << std::endl;	return false;}if (head == NULL){std::cout << "head is NULL" << std::endl;	return false;}//如果node等于headif (head == node){head = head->next;}List *p = head;while (head->next != NULL){if (head->next == node){head->next = head->next->next;std::cout << "delete node success head->value" << head->value << std::endl;//这里要记得把头节点的指针移动最后还原,这里的头节点是保存在这个类里面,改变了就是改变了//如果这里是把head作为参数传递,最后head会被销毁那么不需要移动头指针head = p;return true;}//注意,这里由于head是成员变量,改变了就是改变了,所以需要最后重新指定head = head->next;}std::cout << "delete node fail head->value" << head->value << std::endl;//这里要记得把头节点的指针移动最后还原,这里的头节点是保存在这个类里面,改变了就是改变了//如果这里是把head作为参数传递,最后head会被销毁那么不需要移动头指针head = p;return false;	
}List::List()
{value = 0;head = NULL;next = NULL;
}List::~List()
{delete head;delete next;
}List* List::createNode(int value)
{List *list = NULL;list = new List();if (list){list->value = value;return list;	}return NULL;
}bool List::insertNode(List *node)
{node->next = head;head = node;return true;	
}void List::printList()
{	if (head == NULL){std::cout << "head is NULL" << std::endl;return;}List *p = head;while (p != NULL){std::cout << p->value << std::endl;	p = p->next;}return;	
}void List::printNode()
{std::cout << value << std::endl;	
}int List::listSize()
{if (head == NULL){std::cout << "head is NULL" << std::endl;return 0;	}int len = 0;List *p = head;while (p != NULL){p = p->next;++len;}return len;
}void List::freeList()
{if (head == NULL){std::cout << "head is NULL" << std::endl;return;	}List *p;while (head != NULL){p = head;head = head->next;free(p);}
}int main()
{List list;List *list1 = list.createNode(5);list.insertNode(list1);List *list2 = list.createNode(6);list.insertNode(list2);List *list3 = list.createNode(1);list.insertNode(list3);List *list4 = list.createNode(3);list.insertNode(list4);List *list5 = list.createNode(2);list.insertNode(list5);list.printList();std::cout << "list size is " << list.listSize() << std::endl;std::cout << "-----------开始删除节点值为3的节点" << std::endl;list.deleteNode1(list4);list.printList();std::cout << "list size is " << list.listSize() << std::endl;list.freeList();list.printList();return 0;	
}

 

 

 

 

 

 

3 运行结果

2
3
1
6
5
list size is 5
-----------开始删除节点值为3的节点
delete node success head->value2
2
1
6
5
list size is 4
head is NULL

 

 

 

 

 

 

4 总结

很明显用C语言实现，我们习惯在外面搞个头结点，然后用C++实现，我们直接在类的里面放一个head指针，然后我们在增加节点的时候我们会把head进行移动，放在最前面，所以后面的 便利和删除操作等最好是不要动head的位置了，因为head动了，下次便利就有问题，如果删除函数移动了head，我们最后需要复原head

比如我们的头指针尽量不要移动，我们可以用一个指针变量来保存这个head指针，然后我们移动保存的指针变量，同时把保存的指针变量在一些情况下改变下一个指向的指针，那么我们下次便利head也是生效的，这样保证了头指针不被污染

比如下面的例子

 

#include <stdio.h>void change(char *a)
{*(a + 1) = 's';
}
int main()
{char value[10] = "chenyu";change(value);printf("value is %s\n", value);return 0;
}#include <stdio.h>void change(char *a)
{char *p = a;*(p + 1) = 's';
}
int main()
{char value[10] = "chenyu";change(value);printf("value is %s\n", value);return 0;
}

其实最后的结果都是一样，csenyu

头指针是指向这块内存的地址，如果我们用指针变量保存了，然后这个指针变量也指向了这里，用指针变量去操作后，然后头指针也是指向这里，后面数据的指向也会改变