19.链表插入——头插法

核心思想

1. 当目标节点为第一个节点时

2. 当目标节点为非首节点时

核心代码

1. 当目标节点为第一个节点时

if(p->data==data)
{
	new->next=p;
	
	return new;
}

2. 当目标节点为非首节点时

while(p->next!=NULL)
{
	if(p->next->data==data)
	{
		new->next=p->next;
		p->next=new;
		
		return head;
	}
	p=p->next;
}

return head;

头插法

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

示例

将 99 插入到 1 前，88 插入到 8 前。

#include <stdio.h>

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

void printLink(struct Test* phead)
{

	struct Test* point=phead;
	
	while(point!=NULL)
	{
		printf("%d ",point->data);
		point=point->next;
	}
	putchar('\n');

/*	
	while(1)
	{
		if(phead!=NULL)
		{
			printf("%d ",phead->data);
			phead=phead->next;
		}
		else
		{
			putchar('\n');
			break;
		}
	}
	
*/
}

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

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

void insertBehind(struct Test* phead,int data,struct Test* new)
{
	struct Test* p;
	p=phead;
	
	while(p!=NULL)
	{
		if(p->data==data)
		{
			new->next=p->next;
			p->next=new;
		}
		p=p->next;
	}
}

struct Test* insertFront(struct Test* phead,int data,struct Test* new)
{
	struct Test* p;
	p=phead;
	
	if(p->data==data)
	{
		new->next=p;
		
		return new;
	}
	
	while(p->next!=NULL)
	{
		if(p->next->data==data)
		{
			new->next=p->next;
			p->next=new;
			
			return phead;
		}
		p=p->next;
	}
	return phead; 
}
 
int main()
{	
	struct Test t1={1,NULL};
	struct Test t2={2,NULL};
	struct Test t3={3,NULL};
	struct Test t4={4,NULL};
	struct Test t5={5,NULL};
	struct Test t6={6,NULL};
	struct Test t7={7,NULL};
	struct Test t8={8,NULL};
	
	t1.next=&t2;
	t2.next=&t3;
	t3.next=&t4;
	t4.next=&t5;
	t5.next=&t6;
	t6.next=&t7;
	t7.next=&t8;
	
	printLink(&t1);
	
	int total=0;
	total=totalNodeNum(&t1);
	printf("total num=%d\n",total);
	
	struct Test t100={100,NULL};
	
	insertBehind(&t1,6,&t100);
	printf("after inserting behind:\n");
	printLink(&t1);
	
	struct Test* head=&t1;
	struct Test t99={99,NULL};
	head=insertFront(head,1,&t99);
	printf("after inserting front:\n");
	printLink(head);
	
	struct Test t88={88,NULL};
	head=insertFront(head,8,&t88);
	printf("after inserting front:\n");
	printLink(head);
	
	return 0;
}

运行结果：