单链表逆序操作

Posted 2020-12-03

//逆序操作
//算法1：从第二个节点开始，记录它的下一个节点，然后依次挪到第一个节点之前成为新表头
int inverse_node(struct node pH)
{
struct node p = pH; //头结点
struct node pPrev = NULL; //记录前一个节点
struct node pBack = NULL; //记录下一个节点地址
struct node *pFirstNode = p->pNext; //记录第一个节点

//节点只有1个或者无有效节点时，返回原来的链表，不用进行逆序操作
if((NULL == pFirstNode) | (NULL == pFirstNode->pNext))  
{
    return 0;
}
//节点数两个或以上时
else
{   
    p = p->pNext;           //节点1   
    pBack = p->pNext;       //节点2
    pPrev = p;              //节点1
    p = pBack;              //节点2

    while(NULL != p->pNext)
    {
        pBack = p->pNext;   //节点3
        pH->pNext = p;
        p->pNext = pPrev;
        pPrev = p;
        p = pBack;
    }   
}

pH->pNext = p;
p->pNext = pPrev;

pFirstNode->pNext = NULL;

return 0;

}
运行结果：

整体代码：

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

//单链表的节点模型。
struct node
{
int data;
struct node *pNext;
};

//创建一个节点。
//有效数据为data。
//返回一个指针，该指针指向struct node类型，即创建的节点。
struct node create_node(int data)
{
//malloc申请一段内存来存储数据
struct node p = (struct node *)malloc(sizeof(struct node));

//检验是否申请内存成功
if(NULL == p)
{
    printf("malloc error.
");
    return NULL;
}

p->data = data;
p->pNext = NULL;

return p;

}

//从尾部插入一个新的节点new,pH为头节点
void insert_tail(struct node pH, struct node new)
{
struct node *p = pH;

//让p指向最后一个节点
while(NULL != p->pNext)
{
    p = p->pNext;
}

p->pNext = new;

}

//从头部插入一个新的节点，pH为头节点，new为新插入节点
void insert_head(struct node pH, struct node new)
{
struct node *p = pH;

if(NULL == p->pNext)
{
    p->pNext = new;
}
else
{
    new->pNext = p->pNext;
    p->pNext = new;
}

}

//遍历节点
void ergodic(struct node pH)
{
struct node p = pH;

while(NULL != p->pNext)
{
    p = p->pNext;
    printf("node data is %d
",p->data);
}

}

//删除存储数据为data的节点
void delete_node(struct node pH, int data)
{
struct node p = pH;
struct node *pPrev = NULL;

while(NULL != p->pNext)
{
    pPrev = p;                      //这个指针用来存储上一个节点的地址
    p = p->pNext;                   //p指向下一个节点

    //找到要删除的节点
    if(p->data == data)
    {
        //这个节点是尾节点
        if(NULL == p->pNext)
        {
            pPrev->pNext = NULL;
        }
        //不是尾节点
        else
        {
            pPrev->pNext = p->pNext;
        }

        free(p);                    //删除节点，释放节点的存储空间
    }
}

}

//逆序操作
//算法1：从第二个节点开始，记录它的下一个节点，然后依次挪到第一个节点之前成为新表头
int inverse_node(struct node pH)
{
struct node p = pH; //头结点
struct node pPrev = NULL; //记录前一个节点
struct node pBack = NULL; //记录下一个节点地址
struct node *pFirstNode = p->pNext; //记录第一个节点

//节点只有1个或者无有效节点时，返回原来的链表，不用进行逆序操作
if((NULL == pFirstNode) | (NULL == pFirstNode->pNext))  
{
    return 0;
}
//节点数两个或以上时
else
{   
    p = p->pNext;           //节点1   
    pBack = p->pNext;       //节点2
    pPrev = p;              //节点1
    p = pBack;              //节点2

    while(NULL != p->pNext)
    {
        pBack = p->pNext;   //节点3
        pH->pNext = p;
        p->pNext = pPrev;
        pPrev = p;
        p = pBack;
    }   
}

pH->pNext = p;
p->pNext = pPrev;

pFirstNode->pNext = NULL;

return 0;

}

int main(void)
{
//头指针指向头结点
struct node pHead = NULL;
pHead = create_node(0);
//struct node pHead = create_node(0);

insert_tail(pHead, create_node(11));
insert_tail(pHead, create_node(12));
insert_tail(pHead, create_node(13));
insert_tail(pHead, create_node(14));
insert_tail(pHead, create_node(15));
insert_tail(pHead, create_node(16));
insert_tail(pHead, create_node(17));

ergodic(pHead);

inverse_node(pHead);

printf("------------逆序后------------
");

ergodic(pHead);

/
pHead->pNext = create_node(11);
pHead->pNext->pNext = create_node(12);
pHead->pNext->pNext->pNext = create_node(13);
/
/
printf("node1 data : %d ",pHead->pNext->data);
printf("node2 data : %d ",pHead->pNext->pNext->data);
printf("node3 data : %d ",pHead->pNext->pNext->pNext->data);
/
return 0;
}