C_数据结构_链表

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

//函数声明
PNODE create_list(void)； //创建链表
void traverse_list(PNODE pHead); //输出链表
bool is_empty(PNODE pHead); //判断链表是否为空
int length_list(PNODE); //求连链表的长度
bool insert_list(PNODE, int, int); //插入
bool delete_list(PNODE, int, int *) //删除
void sort_list(PNODE); //排序


typedef struct Node
{
    int data; //数据域;
    struct Node * pNext; //指针域;
}NODE, *PNODE; // NODE等价于struct Node,   PNODE 等价于 struct Node *

int main(void)
{
    PNODE pHead = NULL; //等价于 struct Node * pHead = NULL;
    int val;
    
    pHead = create_list(); //create_list()功能：创建一个非循环单链表，并将该链表的头结点的地址付给pHead
    traverse_list(pHead);
    
    //insert_list(pHead, 4, 33);
    
    if ( delete_list(pHead, 4, &val) )
    {
        printf("删除成功！删除的元素是：%d
", val);
    }
    else
    {
        printf("删除失败！你删除的元素不存在！");
    }
    traverse_list(pHead);
    
    //int len = length_list(pHead);
    //printf("链表的长度是：%d
", len);
    //sort_list(pHead);
    //traverse_list(pHead);
/*
    if ( is_empty(pHead) )
            printf("链表为空！
");
        else
            printf("链表不空！");
*/        
    
    return 0;
}

PNODE create_list(void) //创建链表
{
    int len; //用来存放有效节点的个数
    int i;
    int val; //用来临时存放用户输入的节点值
    
    //分配了一个不存放有效数据的头结点
    PNODE pHead = (PNODE)malloc(sizeof(NODE));
    if (NULL == pHead)
    {
        printf("分配失败！程序终止！
");
        exit(-1); 
    }
    
    PNODE pTail = pHead;
    pTail->pNext = NULL;
    
    printf("请输入输入您需要生成的链表节点的个数：len = ");
    scanf("%d", &len);
    
    for (i=0; i<len; ++i)
    {
        printf("请输入第%d个节点的值：", i+1);
        scanf("%d", &val);
        
        PNODE pNew = (PNODE)malloc(sizeof(NODE));
        if (NULL == pNew)
        {
            printf("分配失败！程序终止！
");
            exit(-1); 
        }
        pNew->data = val;
        pTail->pNext = pNew;
        pNew->pNext = NULL;
        pTail = pNew;
        
    }
    
    return pHead;
}

void traverse_list(PNODE pHead) //输出链表
{
    PNODE p = pHead->pNext;
    
    while (NULL != p)
    {
        printf("%d ", p->data);
        p = p->pNext;
    }
    printf("
");
    
    return;
}

bool is_empty(PNODE pHead); //判断链表是否为空
{
    if (NULL == pHead->pNext)
        return true;
    else
        return false;
}

int length_list(PNODE); //求连链表的长度
{
    PNODE p = pHead->pNext;
    int len = 0;
    
    while (NULL != p)
    {
        ++len;
        p = p->pNext;
    }
    
    return len;
}

void sort_list(PNODE); //排序
{
    int i, j, t;
    int len = length_list(pHead);
    PNODE p, q;
    
    for (i=0,p=pHead->pNext; i<len-1; ++i,p=p->pNext)
    {
        for (j=i+1,q=p->pNext; j<len; ++j,q=q->pNext)
        {
            if (p->data > q->data)  //类似数组中的：if (a[i] > a[j])
            {
                t = p-data;
                p->data = q->data;
                q->data = t;
            }
        }
    }
    
/*    数组的冒泡排序
    for (i=0; i<len-1; ++i)
    {
        for (j=i+1; j<len; ++j)
        {
            if (a[i] > a[j])
            {
                t = a[i];
                a[i] = a[j];
                a[j] = t;
            }
        }
    }
*/

}

//在pHead所指向链表的第pos个节点的前面插入一个新的节点，该节点的值是val，并且pos的值是从1开始
bool insert_list(PNODE pHead, int pos, int val); //插入
{
    int i = 0;
    PNODE p = pHead;
    
    while (NULL!=p && i<pos-1)
    {
        p = p->pNext;
        ++i;
    }
    
    if (i>pos-1 || NULL==p) // i>pos-1 保证了 pos 大于等于1
        return false;
    
    PNODE pNew = (PNODE)malloc(sizeof(NODE));
    if (NULL == pNew)
    {
        printf("动态内存分配失败！
");
        exit(-1);
    }
    pNew->data = val;
    PNODE q = p->pNext;
    p->pNext = pNew;
    pNew->pNext = q;
    
    return true;
}

bool delete_list(PNODE, int pos, int * pval) //删除
{
    int i = 0;
    PNODE p = pHead;
    
    while (NULL!=p->pNext && i<pos-1)
    {
        p = p->pNext;
        ++i;
    }
    
    if (i>pos-1 || NULL==p->pNext)
        return false;
    
    PNODE q = p->pNext;
    *pVal = q->data;
    
    //删除p后面的节点
    p->pNext = p->pNext->pNext; //p->pNext->pNext 等价于 q->pNext
    free(q);
    q = NULL;
    
/*
    * pval = p->pNext->data;
    p->pNexp = p->pNext->pNext;
*/
    
    return true;
}