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

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

//創(chuàng)建一個結(jié)點
Node *createNode(){
    //創(chuàng)建一個新德頭結(jié)點
    Node *pTemp = (Node *)malloc(1 * sizeof(Node));
    if (pTemp == NULL) {
        return NULL;
    }
    
    //賦初值
    pTemp->previous = NULL;
    pTemp->next = NULL;
    pTemp->age = 0;

    //返回這個結(jié)點的地址
    return pTemp;
}

//創(chuàng)建頭結(jié)點
bool createHeader(Node **pHeader){
    //創(chuàng)建一個新德頭結(jié)點
    *pHeader = createNode();
    
    if (pHeader == NULL) {
        return false;
    } else {
        return true;
    }
}

//是否繼續(xù)
bool isContinue(){
    char option;
    do {
        getchar();
        printf("是否繼續(xù)添加(y/n)?：");
        option = getchar();
    } while (option != 'y' && option != 'n');
    
    if (option == 'y') {
        return true;
    } else{
        return false;
    }
}

//initial
void initial(Node * const pHeader){
    Node *pTail = pHeader;
    
    //添加保存數(shù)據(jù)的結(jié)點
    while (1) {
        //需要創(chuàng)建一個結(jié)點
        Node *pTemp = createNode();
        if (pTemp == NULL) {
            exit(EXIT_FAILURE);
        }
        printf("請輸入年齡:");
        scanf("%d", &pTemp->age);
        
        //判斷添加的位置
        if (pHeader->next == NULL) {
            //頭結(jié)點指向第一個結(jié)點
            pHeader->next = pTemp;
            
            //第一個結(jié)點的previous指向頭結(jié)點
            pTemp->previous = pHeader;
            
            //第一個結(jié)點的next指向頭結(jié)點
            pTemp->next = pHeader;
            
            //頭結(jié)點的previou指向第一個結(jié)點
            pHeader->previous = pTemp;
            
            //pTail指針指向第一個結(jié)點
            pTail = pTemp;
            
        } else{
            //前面已經(jīng)存在結(jié)點了
            //讓尾結(jié)點的next指向pTemp
            pTail->next = pTemp;
            
            //讓pTemp的previous指針指向目前的尾結(jié)點
            pTemp->previous = pTail;
            
            //讓pTail指向最后一個結(jié)點pTemp
            pTail = pTemp;
            
            //尾結(jié)點的next指針指向頭結(jié)點
            pTail->next = pHeader;
            
            //頭結(jié)點的previous指針指向尾結(jié)點
            pHeader->previous = pTail;
        }
        
        //提問是否繼續(xù)
        if (isContinue() == false){
            break;
        }
    }
   
}

//輸出鏈表的內(nèi)容
void show(const Node * const pHeader){
    Node *pTemp = pHeader->next;
    
    while (pTemp != NULL) {
        printf("%d ", pTemp->age);
        pTemp = pTemp->next;
        
        if (pTemp == pHeader) {
            break;
        }
    }
    printf("\n");
}

//獲取index對應(yīng)的結(jié)點的地址
Node *addressOfIndex(Node *pHead, int index){
    Node *pTemp = pHead->next;
    
    while (index > 0) {
        if (pTemp == pHead) {
            //節(jié)點數(shù)少于index
            break;
        }else{
            pTemp = pTemp->next;
        }
        
        index--;
    }
    
    if (index > 0) {
        printf("刪除的元素不存在\n");
        return NULL;
    }else{
        //讓pTemp指向即將被我刪除的那個結(jié)點
        pTemp = pTemp->previous;
        return pTemp;
    }
}

//插入一個元素
//刪除
void delete(Node *pHead, int index){
    //獲取index對應(yīng)的結(jié)點的地址
    Node *pIndex = addressOfIndex(pHead, index);
    
    if (pIndex == NULL) {
        printf("刪除的元素不存在\n");
        exit(EXIT_FAILURE);
    } else{
        //讓index前面的結(jié)點next指針指向index后面的結(jié)點
        pIndex->previous->next = pIndex->next;
        
        //讓index后面的結(jié)點的previous指針指向index前面的結(jié)點
        pIndex->next->previous = pIndex->previous;
        
        free(pIndex);
    }
}

void insert(Node *pHeader, int index, int element){
    //首先獲取index對應(yīng)的結(jié)點的地址
    Node *pIndex = addressOfIndex(pHeader, index);
    if (pIndex == NULL) {
        printf("刪除的元素不存在\n");
        exit(EXIT_FAILURE);
    } else{
        //在index的前面插入一個元素
        //為這個元素分配內(nèi)存空間
        Node *pNew = createNode();
        if (pNew == NULL) {
            exit(EXIT_FAILURE);
        }else{
            pNew->age = element;
            
            //讓new結(jié)點的next指針指向pIndex
            pNew->next = pIndex;
            
            //讓new結(jié)點的previous指針指向index前面一個結(jié)點的地址
            pNew->previous = pIndex->previous;
            
            //讓pIndex德previous指向pnew
            pIndex->previous = pNew;
            
            //讓index前面的結(jié)點的next指向pNew
            pNew->previous->next = pNew;
        }
    }
}

int main(int argc, const char * argv[]) {
    
    //定義一個指針 指向頭結(jié)點（頭結(jié)點不存數(shù)據(jù)）
    Node *pHead = NULL;
    
    //創(chuàng)建頭結(jié)點
    if (createHeader(&pHead) == false) {
        //創(chuàng)建頭結(jié)點出錯了线罕。
        exit(EXIT_FAILURE);
    }
    
    //初始化這個雙鏈表
    initial(pHead);
    
    show(pHead);
    
    delete(pHead, 3);
    
    show(pHead);
    
    insert(pHead, 2, 100);
    
    show(pHead);
    return 0;
}