9.3 链表从指定节点插入新节点

一、从指定节点后方插入

插入逻辑如图：

插入前：A指向B，B指向C

插入后：B为插入点，当要插入D时就要让B指向D，D再指向C（插入前B的指向）

#include 

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

void printLink(struct Test *head)
{
	while(1){
		if(head != NULL){
		printf("%d ",head->data);
		head = head->next;
		}else{
			printf("\n");
			break; 
		}
	}
}

int getLinkNum(struct Test *head)
{
	int cnt =0;
	while(head !=NULL){
		cnt ++;
		head = head->next;
	}
	return cnt;
}

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

int insertBhind(struct Test *head,int data,struct Test *new)
{
	struct Test *p = head;        
	while(p !=NULL){
		if(p->data == data){
			new->next = p->next;    //新插入的链表指向插入点的链表
			p->next = new;          //插入点指向新插入的链表
			return 1;    
		}
		p = p->next;                //循环结束，p指向后面的链表
	}
	return 0;
}
int main(){
	struct Test t1 = {1,NULL};
	struct Test t2 = {2,NULL};
	struct Test t3 = {3,NULL};
	struct Test t4 = {4,NULL};
	
	t1.next = &t2;
	t2.next = &t3;
	t3.next = &t4;
	
	printLink(&t1);
	int ret =getLinkNum(&t1);
	printf("total num = %d\n",ret);
	
	ret = searchLink(&t1,1);
	if(ret = 0){
		printf("没有data = 1\n");
	}else{
		printf("有data = 1\n");
	}
	
	struct Test new={100,NULL};      //定义“new”链表
	insertBhind(&t1,3,&new);        //在数据等于3的位置插入“new”链表
	printLink(&t1);
	return 0;
}

二、从指定节点前方插入

插入逻辑如图：

插入前：A指向B，B指向C

插入后：B为插入点，当要插入D时就要让A指向D，D再指向B（插入前A的指向）

①当插入点为链表头：

那么就要找到链表头，让新链表指向当前的链表头，而新链表头顺位称为新的链表头，使其插入最前端。

struct Test* insertAhead(struct Test *head,int data,struct Test *new)
{
	if(head->data == data){
		new->next=head;
		return new;
	}
}

	struct Test *head = &t1;
	printLink(&t1);
	
	
	
	struct Test new2={200,NULL};
	head = insertAhead(head,1,&new2);
	puts("after insert ahead:\n");
	printLink(head);

输出结果：

1 2 3 4
after insert ahead:

200 1 2 3 4

②任意位置插入新链表

 目标插入位置是插入链表的目标指向，而目标插入位置的前一位就指向了新插入的链表

#include 

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

void printLink(struct Test *head)
{
	while(1){
		if(head != NULL){
		printf("%d ",head->data);
		head = head->next;
		}else{
			printf("\n");
			break; 
		}
	}
}

int getLinkNum(struct Test *head)
{
	int cnt =0;
	while(head !=NULL){
		cnt ++;
		head = head->next;
	}
	return cnt;
}

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


struct Test* insertAhead(struct Test *head,int data,struct Test *new)
{
	struct Test *p = head;       //定义一个新的指针变量
	if(head->data == data){
		new->next=p;
		return new;
	}
	while(p->next != NULL){     //寻找目标数据进行插入
		if(p->next->data == data){
			new->next = p->next;
			p->next = new;
			return head;        //返回初始链表头
		}
		p = p->next;
		
	}
	printf("no this data\n");
}
int main(){
	struct Test t1 = {1,NULL};
	struct Test t2 = {2,NULL};
	struct Test t3 = {3,NULL};
	struct Test t4 = {4,NULL};
	
	t1.next = &t2;
	t2.next = &t3;
	t3.next = &t4;
	
	struct Test *head = &t1;
	printLink(&t1);
	
	
	
	struct Test new1={200,NULL};
	head = insertAhead(head,1,&new1);
	puts("after insert head:\n");
	printLink(head);
	
	struct Test new2={400,NULL};        //在3前面插入400
	head = insertAhead(head,3,&new2);
	puts("after insert ahead:\n");
	printLink(head);
	return 0;
}