单向链表的三种插入方式#链表#单项链表_单链表插入

链表

单项链表一般有三种插入方式

1.头插，在头节点后，首节点前插入

 2.尾插，从末尾插入

 3.从任意位置插入

int input_func(Link *pHead,int pos,data_type item)
{
	int i;
	if(NULL == pHead)
	{
		perror("pHead_NULL");
		return -1;
	}
	Link *pNew = NULL;
	pNew = (Link *)malloc(sizeof(Link));
	if(NULL == pNew)
	{
		perror("pNew_MALLOC_ERROR!");
		return -1;
	}
	Link *pPre = NULL;
	//定义一个位置插入
	Link *pTail = NULL;
	switch(pos)
	{
		//首插法
		case 1:
			if(pHead->pNext != NULL)
			{
				pNew->pNext = pHead->pNext;
			}
			pHead->pNext = pNew;
			pNew->data = item;
			break;
		//尾插法
		case -1:
			pTail = pHead;
			while(pHead->pNext != NULL)
			{
				pTail = pTail->pNext;
			}
			pTail->pNext = pNew;
			pNew->data = item;
			break;
		//从任意位置插入
		case 2:
			pPre = pHead;
			//找到要插入节点的前一个节点
			//当pPre不为空的情况下移动pos-1次
			while(pPre != NULL & i<pos-1)
			{
				pPre = pPre->pNext;
				i++;
			}
			//保护插入节点后的所有节点 
			pNew->pNext = pNew;
			//插入
			pPre->pNext=pNew;
			break;
	}
	return 0;
}