19 链表基本操作

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>       //exit 函数需要
#include <malloc.h>

typedef struct node
{
    struct node* pNext;
    int data;            
}*PNODE,NODE;               //PNODE ==struct node *  ,       NODE==struct node

//函数原型
PNODE  create_list(void);
bool is_empty(PNODE);
void traverse_list(PNODE);
int lenth_list(PNODE);
bool insert_list(PNODE, int val, int index);
bool delete_list(PNODE, int index, int* val);
void sort_list(PNODE);


//测试程序
main() {
    PNODE pHead = NULL;            //定义空指针；

    pHead = create_list();
    is_em = is_empty(pHead);
    //insert_list(pHead, 11, 3);
    delete_list(pHead, 2, &delval);
    traverse_list(pHead);
    printf("\n  delval=%d", delval);
}
 PNODE create_list(void) {
    int len;
    int i;
    int val;

    PNODE pHead = (PNODE)malloc(sizeof(NODE));      //动态申请一个NODE的内存，pHead指向这个内存  ①
    PNODE pTail = pHead;            // pHead复制一个, pTail开始创造list     ②
    pTail->pNext = NULL;               //pTail后面没有结点,现在有两个结点，没数据   ③

    if (NULL == pHead) {             //内存申请失败
        printf("Creat list ERROR !!   ");
    }

    printf("Please Enter the  Lenth of the List , Lenth=   ");
    scanf_s("%d", &len);

    for (i = 0; i < len; i++) {

        PNODE pNew= (PNODE)malloc(sizeof(NODE));   // 申请一个new NODE的内存 ④
        printf("Please the %dth Value of List :   ",i+1);
        scanf_s("%d", &val);

        pNew->data = val;                    //链表赋值 ⑤
        pTail->pNext = pNew;                 //pNew连上pTail ⑥
        pNew->pNext= NULL;            　　　　//  ⑦　　　　　
        pTail = pNew;                       //pNew 变成pTail ⑧

    }
    return pHead ;
}

bool is_empty(PNODE pHead) {
    bool is_em = false;
    if (NULL == pHead->pNext )
        is_em = true;

    return is_em;
}
void traverse_list(PNODE pHead) {
    int len=0;
    PNODE p;

    if (is_empty(pHead))
        printf("The list is Empty!! \n");
    else {
        p = pHead->pNext;
        do {
            printf("%d", p->data);
            p = p->pNext;
            len++;
        } while (p!= NULL);

    }
    
    printf("\nList lenth =%d ", len);


}

创建链表算法：

 

bool insert_list(PNODE pHead, int val, int index) {
    PNODE p = pHead;
    int i = 0;

    PNODE pNew = (PNODE)malloc(sizeof(NODE));
    while (NULL != p && i < index - 1) {
        p = p->pNext;
        i++;
    }

    if (NULL == p || i < index - 1)
        return false;
    pNew->data = val;
    pNew->pNext = p->pNext;
    p->pNext = pNew;
}

bool delete_list(PNODE pHead, int index, int* val) {
    PNODE p = pHead;
    PNODE r;
    int i = 0;
    *val = -1;       //如果删除失败val就为-1，还是有点问题
    while (NULL != p->pNext && i < index - 1) {
        p = p->pNext;
        i++;
    }

    if (NULL == p->pNext || i > index - 1) 
        return false;


    //先让r指向要删除的node，然后free r，防止内存泄漏
        //三个node顺序为  p---要删除的（r）--- r->pNext

        r = p->pNext;
        *val = r->data;                //带回删除的数
        p->pNext = r->pNext;
        //    p->pNext = p->pNext->pNext;
        free(r);
        r = NULL;