2015.12.16 doubleLinkedList-Function

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

typedef struct node{
    struct node *previous;
    int age;
    struct node *next;
}Node;

//创建一个结点
Node *createNode();
//初始化链表
void intial(Node *const pHead);
//是否继续
bool isContinue();
//查找index对应的结点位置
Node *checkIndex(Node *pHead, int index);
//输出链表
void show(const Node *const pHead);
//插入结点
void insert(Node *pHead, int index, int element);
//删除结点
void delete(Node *pHead, int index);

int main(int argc, const char * argv[]) {
    //定义一个指针 指向头结点(头结点不存储数据)
    Node *pHead = NULL;
    
    pHead = createNode();
    if (pHead == NULL) {
        exit(EXIT_FAILURE);
    }
    
    intial(pHead);
    
    show(pHead);
    
    insert(pHead, 3, 99);
    
    show(pHead);
    
    delete(pHead, 3);
    
    show(pHead);
    
    return 0;
}



Node *createNode(){
    //创建一个新的结点
    Node *pTemp = (Node *)malloc(sizeof(Node));
    if (pTemp == NULL) {
        return NULL;
    }
    
    //赋初值
    pTemp->previous = NULL;
    pTemp->next = NULL;
    
    //返回
    return pTemp;
}

void intial(Node *const pHead){
    Node *pTail = pHead;
    
    //添加保存数据的结点
    while (1) {
        Node *pTemp = createNode();
        if (pTemp == NULL) {
            exit(EXIT_FAILURE);
        }
        //输入数据
        printf("Please input age:");
        scanf("%d", &pTemp->age);
        
        //判断需要添加的位置
        if (pHead->next == NULL) {
            //头指针指向第一个结点
            pHead->next = pTemp;
            
            //第一个结点的previous指针指向头结点
            pTemp->previous = pHead;
            
            //第一个结点的next指针指向头指针
            pTemp->next = pHead;
            
            //头指针的previous指向第一个结点
            pHead->previous = pTemp;
            
            //尾指针指向第一个结点
            pTail = pTemp;
        } else{
            //前面的结点已经存在了
            //让尾结点的next指向新建的结点
            pTail->next = pTemp;
            
            //新建结点的previous指针指向尾结点
            pTemp->previous = pTail;
            
            //pTail指向新建的结点
            pTail = pTemp;
            
            //尾结点的next指针指向头结点
            pTail->next = pHead;
            
            //头结点的previous指针指向尾结点
            pHead->previous = pTail;
        }
        //询问是否继续
        if (isContinue() == false) {
            break;
        }
    }
    
    
}

bool isContinue(){
    char option;
    do {
        getchar();
        printf("Is continued(y/n):");
        option = getchar();
    } while (option != 'y' && option != 'n');
    
    if (option == 'y') {
        return true;
    } else{
        return false;
    }
}

void show(const Node *const pHead){
    Node *pTemp = pHead->next;
    
    while (pTemp != NULL) {
        printf("%d ", pTemp->age);
        pTemp = pTemp->next;
        
        if (pTemp == pHead) {
            break;
        }
    }
    printf("\n");
}

Node *checkIndex(Node *pHead, int index){
    Node *pTemp = pHead->next;
    
    while (index > 0) {
        if (pTemp == pHead) {
            //结点数少于index
            break;
        } else{
            pTemp = pTemp->next;
        }
        index --;
    }
    if (index > 0) {
        return NULL;
    } else{
        //让pTemp指向上一个结点（因为while循环中『指过了』）
        pTemp = pTemp->previous;
        return pTemp;
    }
}

void insert(Node *pHead, int index, int element){
    //首先应该获取到index对应的结点地址
    Node *pIndex = checkIndex(pHead, index);
    
    if (pIndex == NULL) {
        printf("相应的元素不存在\n");
        exit(EXIT_FAILURE);
    } else{
        //在index前插入一个指针，并且为这个指针分配内存
        Node *pNew = createNode();
        
        if (pNew == NULL) {
            exit(EXIT_FAILURE);
        } else{
            pNew->age = element;
            
            //pNew的next指针指向pIndex
            pNew->next = pIndex;
            
            //pNew的previous指针指向pIndex前面的那个结点的地址
            pNew->previous = pIndex->previous;
            
            //pIndex前面的那个结点的next指针指向pNew
            pIndex->previous->next = pNew;
            
            //pIndex的previous指针指向pNew
            pIndex->previous = pNew;
        }
    }
}

void delete(Node *pHead, int index){
    //获取到index对应的结点
    Node *pIndex = checkIndex(pHead, index);
    
    if (pIndex == NULL) {
        exit(EXIT_FAILURE);
    } else{
        //pIndex前面结点的next指针指向pIndex后面的结点
        pIndex->previous->next = pIndex->next;
        
        //pIndex后面结点的previous指针指向pIndex前面的结点
        pIndex->next->previous = pIndex->previous;
        
        //释放pIndex结点
        free(pIndex);
    }
}