链表学习.

1.链表也是一种数据结构

对比与之前的数组来说，数组的元素地址是连续的，增删改查比较麻烦，处理元素不够灵活。

#include

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

int main()
{
	struct Test t1 = {1,NULL};
	struct Test t2 = {2,NULL};
	struct Test t3 = {3,NULL};


	t1.next = &t2;
	t2.next = &t3;
	
	printf("%d %d %dn",t1.data,t1.next->data,t1.next->next->data);
	
	return 0;
	
}

2.链表遍历

void printTest(struct Test *head)
{
	struct Test *point;
	point = head;
	
	while(point != NULL)
	{
		if(point != NULL)
		{
			printf("%d ",point->data);
			point = point->next;
		}
	}
}

3.统计链表个数

int countTest(struct Test *p)
{
	int cnt;
	
	while(p != NULL)
	{
		if(p != NULL)
		{
			cnt++;
			p = p->next;
		}
	}
	return cnt;
}

4.查找链表元素

int searchTest(struct Test *t,int data)
{
	
	while(t != NULL)
	{
		if(t->data == data)
		{
			return 1;
		}
		t =t->next;
	}
	return 0;
}

5.从对应节点后方插入新元素

int insertTestforbehind(struct Test *head,int data,struct Test *new)
{
	struct Test *point;
	point = head;
	
	while(point != NULL)
	{
		if(point->data == data)
		{
			new->next = point->next;   
			point->next = new;
			return 1;
		}
		point = point->next;
	}
	
	return 0;
}

            new->next = point->next;   
			point->next = new;

需要先指向原先数组的下一项，不能颠倒，否则下一项没有东西可以指向。

6.从对应节点前方插入新节点：从头节点；从中间节点

struct Test* insertTestforhead(struct Test *head,int data,struct Test *new)
{
	struct Test *p;
	p = head;
	
	if(p->data == data)     //如果是在头部位置
	{
		new->next = p;   
		return new;
	}
	
	while(p->next != NULL)   //头部下一个位置
	{
		if(p->next->data == data)
		{
			new->next = p->next;
			p->next = new;
			return head;
		}
		p = p->next;
	}
	
	return 0;
	
}

7.删除指定节点：头节点；中间节点

头节点：直接把头值赋给下一个

中间节点：绕过需要删除的节点，把下个地址直接赋值给下下个地址

struct Test* deleteNode(struct Test *head,int data)
{
	struct Test *p;
	p = head;
	
	if(p->data == data)
	{
		head = head->next;
		return head;
	}
	while(p->next != NULL)
	{
		if(p->next->data == data)
		{
			p->next = p->next->next;
			return head;
		}
		p = p->next;
	}
	return head;
}