链表指定位置插入，指定位置删除，逆置链表的练习

指定位置插入：
insert_pos_val(lk headNode, int pos, int val)；

#define _CRT_SECURE_NO_WARNINGS
#include
#include
typedef struct LinkNode
{
     
	int num;
	LinkNode* next;
}Lk, * lk;
//初始化头节点
lk init_headNode()
{
     
	lk headNode = (lk)malloc(sizeof(Lk));
	if (headNode == NULL)
	{
     
		return NULL;
	}
	headNode->next = NULL;
	//指针遍历输出
	lk endNode = headNode;
	//输入-1结束向链表赋值
	int val = -1;
	while (1)
	{
     
		printf("请输入：\n");
		scanf("%d", &val);
		if (val == -1)
		{
     
			break;
		}
		lk newNode = (lk)malloc(sizeof(Lk));
		newNode->num = val;
		newNode->next = NULL;
		//尾插法
		endNode->next = newNode;
		endNode = newNode;
	}
	return headNode;
}
//遍历输出
void foreach_linkList(lk headNode)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk curNode = headNode->next;
	while (curNode)
	{
     
		printf("%d\n", curNode->num);
		curNode = curNode->next;
	}
}
//指定位置插入一个值
void insert_pos_val(lk headNode, int pos, int val)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk prveNode = headNode;
	lk curNode = headNode->next;
	//索引
	int index = 0;
	while (curNode)
	{
     
		if (index == pos)
		{
     
			break;
		}
		prveNode = curNode;
		curNode = curNode->next;
		index++;
	}
	if (pos > index)
	{
     
		printf("无法插入当前位置\n");
		return;
	}
	lk newNode = (lk)malloc(sizeof(Lk));
	newNode->num = val;
	newNode->next = NULL;
	prveNode->next = newNode;
	newNode->next = curNode;
}
int main()
{
     
	lk headNode = init_headNode();
	printf("打印输出链表：\n");
	foreach_linkList(headNode);
	printf("插入后打印输出链表：\n");
	insert_pos_val(headNode, 10, 521);
	foreach_linkList(headNode);
	return 0;
}

指定位置删除：

#define _CRT_SECURE_NO_WARNINGS
#include
#include
typedef struct LinkNode
{
     
	int num;
	LinkNode* next;
}Lk, * lk;
//初始化头节点
lk init_headNode()
{
     
	lk headNode = (lk)malloc(sizeof(Lk));
	if (headNode == NULL)
	{
     
		return NULL;
	}
	headNode->next = NULL;
	//指针遍历输出
	lk endNode = headNode;
	//输入-1结束向链表赋值
	int val = -1;
	while (1)
	{
     
		printf("请输入：\n");
		scanf("%d", &val);
		if (val == -1)
		{
     
			break;
		}
		lk newNode = (lk)malloc(sizeof(Lk));
		newNode->num = val;
		newNode->next = NULL;
		//尾插法
		endNode->next = newNode;
		endNode = newNode;
	}
	return headNode;
}
//遍历输出
void foreach_linkList(lk headNode)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk curNode = headNode->next;
	while (curNode)
	{
     
		printf("%d\n", curNode->num);
		curNode = curNode->next;
	}
}
//指定位置删除
void delete_pos_val(lk headNode, int pos, int val)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk prveNode = headNode;
	lk curNode = headNode->next;
	//索引：跟据curNode位置移动
	int index = 1;
	while (curNode)
	{
     
		if (index == pos)
		{
     
			break;
		}
		prveNode = curNode;
		curNode = curNode->next;
		index++;
	}
	if (pos > index)
	{
     
		printf("没有当前元素可供删除\n");
		return;
	}
	//改变prveNode指针指向
	prveNode->next = curNode->next;
	//释放curNode节点在堆区开辟的数据
	free(curNode);
}
int main()
{
     
	lk headNode = init_headNode();
	printf("打印输出链表：\n");
	foreach_linkList(headNode);
	printf("删除后打印输出链表：\n");
	delete_pos_val(headNode, 2, 521);
	foreach_linkList(headNode);
	return 0;
}

逆置链表方式：只对当前链表进行操作，不借用新链表

#define _CRT_SECURE_NO_WARNINGS
#include
#include
typedef struct LinkNode
{
     
	int num;
	LinkNode* next;
}Lk, * lk;
//初始化头节点
lk init_headNode()
{
     
	lk headNode = (lk)malloc(sizeof(Lk));
	if (headNode == NULL)
	{
     
		return NULL;
	}
	headNode->next = NULL;
	//指针遍历输出
	lk endNode = headNode;
	//输入-1结束向链表赋值
	int val = -1;
	while (1)
	{
     
		printf("请输入：\n");
		scanf("%d", &val);
		if (val == -1)
		{
     
			break;
		}
		lk newNode = (lk)malloc(sizeof(Lk));
		newNode->num = val;
		newNode->next = NULL;
		//尾插法
		endNode->next = newNode;
		endNode = newNode;
	}
	return headNode;
}
//遍历输出
void foreach_linkList(lk headNode)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk curNode = headNode->next;
	while (curNode)
	{
     
		printf("%d\n", curNode->num);
		curNode = curNode->next;
	}
}
//逆置链表
void reverse_pos_val(lk headNode)
{
     
	if (headNode == NULL)
	{
     
		return;
	}
	lk prveNode = headNode;
	lk curNode = prveNode->next;
	lk nextNode = curNode->next;
	//第一步：
	prveNode->next = NULL;
	curNode->next = NULL;
	//第二步到第五步
	while (nextNode != NULL)
	{
     
		//辅助指针往后移动
		prveNode = curNode;
		curNode = nextNode;
		nextNode = nextNode->next;
		//移动过后改变链表中curNode节点next指针指向
		curNode->next = prveNode;
	}
   //第六步
	headNode->next = curNode;	
}
int main()
{
     
	lk headNode = init_headNode();
	printf("打印输出链表：\n");
	foreach_linkList(headNode);
	printf("逆置后打印输出链表：\n");
	reverse_pos_val(headNode);
	foreach_linkList(headNode);
	return 0;
}

方式二：准备一个新链表，取出之前链表中的元素，用头插法的方式插入新准备的链表中，这里不做演示