C单链表操作

今天面试给“宇龙酷派”鄙视了。我想说，其实链表反转我会！

单链表：初始化、创建、显示、删除、插入特定位置、删除特定位置、反转操作。

#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <string.h>

typedef struct student
{
	int data;
	struct student* next;
}Node;

//初始化
Node* InitNode()
{
	Node* head;
	head = (Node*)malloc(sizeof(Node));
	if (NULL == head)
	{
		printf("Failed to initialize.\n");
		return NULL;
	}

	head->next = NULL;
}

//输入数据
Node* CreatNode(Node* head)
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return NULL;
	}
	Node* pre = head;
	printf("CreatNode: enter a data:\n");
	int itmp;
	while (scanf("%d", &itmp))  //ctrl+z  结束
	{
		Node* tmp;
		tmp = (Node*)malloc(sizeof(Node));
		if (NULL == tmp)
		{
			printf("Initialize new node fail.\n");
			return head;
		}

		tmp->data = itmp;
		tmp->next = NULL;

		pre->next = tmp;
		pre = tmp;
	}

	return head;
}

//显示
Node* PrintNode(Node* head)
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return NULL;
	}
	Node* pre = head->next;
	printf("The list is:\n");
	while (pre)
	{
		printf("%d ", pre->data);
		pre = pre->next;
	}
	printf("\n");
	return head;
}

//计算
int CalcNode(Node* head)
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return 0;
	}
	Node* pre = head->next;
	int num = 0;
	while (pre)
	{
		num++;
		pre = pre->next;
	}
	return num;
}

//删除
void DelNode(Node* head)
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		exit(1);
	}
	
	Node* delp = head->next;	
	while (delp)
	{
		Node* tmp = delp->next;
		free(delp);
		delp = tmp;
	}
	printf("The head is cleared.\n");
}

//删除指定某个
Node* DelposNode(Node* head, int pos) //pos = 0,1,2..
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return NULL;
	}
	if (pos > CalcNode(head))
	{
		printf("The position is illegal.\n");
		return NULL;
	}
	Node* p1 = head;
	Node* p2 = p1->next;
	Node* p3 = p2->next;
	int itmp = pos;
	while (itmp != 0)
	{
		p1 = p1->next;
		p2 = p1->next;
		p3 = p2->next;
		itmp--;
	}
	if (p2 != NULL)
	{
		free(p2);
		p1->next = p3;
	}

	return head;
}

//反转：1、保存原先链表，并while遍历
//	   2、取出head节点做新链表头
//	   3、利用头插入法将取出的原先元素存入新表中
Node* ReverseNode(Node* head)
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return NULL;
	}

	Node* oldnow = head->next;  //遍历原先链表 节点
	head->next = NULL;			//原先链表清空，取出head节点
	while (oldnow)
	{
		Node* tmp = oldnow->next; //保存oldnow后一个节点

		/*头插法插入新节点*/
		Node* newtmp = head->next;  
		head->next = oldnow;       //放入新链表head后面
		head->next->next = newtmp;  //确保链接还原    

		oldnow = tmp;			   //now跳入原先链表的下个节点
	}
	
	return head;
}

//插入
Node* InserNode(Node* head, int pos, int data) //pos = 1，2，..
{
	if (NULL == head)
	{
		printf("The head is NULL.\n");
		return NULL;
	}
	if (pos > CalcNode(head))
	{
		printf("The position is illegal.\n");
		return NULL;
	}
	
	Node* pre = head;
	Node* now = pre->next;
	int num = pos;
	while (pos--)  //寻找到位置
	{
		pre = pre->next;
		now = now->next;
	}
	if (now != NULL)  //now为当前插入的位置
	{
		Node* newp = (Node*)malloc(sizeof(Node));
		newp->data = data;      
		
		pre->next = newp;       //重新拼接，把now接上新的节点newp后
		pre->next->next = now;
	}

	return head;
}
int main(void)
{
	Node* head = InitNode();
	CreatNode(head);
	PrintNode(head);
	InserNode(head, 0, 100);
	PrintNode(head);
	//Delete
	DelNode(head);
//	PrintNode(head);
	return 0;
}