单链表的创建，查找，删除，顺序打印，倒序打印（剑指offer）

单链表的创建，查找元素，删除元素，顺序打印单链表元素，逆序（倒序）打印单链表元素。

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#include <cassert>#include <iostream>//默认不使用栈实现反序打印链表中的元素#define USE_STACK 0#if USE_STACK#include <stack>#endifstruct ListNode{    int mVal;    ListNode* mpNext;};/***@pHead 使用指针的指针，使得函数结束后pHead指向的节点有效*@val 待插入的值*/void addNodeToTail(ListNode** pHead, int val){    ListNode* pNewNode = new ListNode;    pNewNode->mVal = val;    pNewNode->mpNext = nullptr;    //如果头节点为空    if (*pHead == nullptr)    {        *pHead = pNewNode;    }    else    {    ListNode* pNode = *pHead;    while (pNode->mpNext != nullptr)        pNode = pNode->mpNext;        pNode->mpNext = pNewNode;    }}void destroyList(ListNode** pHead){   std::cout << "\nstart free memery..." << std::endl;    ListNode* pNode = *pHead;    while (*pHead != nullptr)    {            *pHead = (*pHead)->mpNext;        delete pNode;        pNode = *pHead;    }    std::cout << "free memery complete" << std::endl;}//从头到尾打印链表void printList(ListNode**pHead){    ListNode *pNode =*pHead;    while (pNode != nullptr)    {        std::cout << pNode->mVal << " ";    pNode = pNode->mpNext;    }}//从尾到头打印链表，使用递归实现且不该变原列表的结构void printReverseList(ListNode* pHead){    if (pHead != nullptr)    {        if (pHead->mpNext != nullptr)    {        printReverseList(pHead->mpNext);    }    std::cout << pHead->mVal << "\t";    }}#if USE_STACKvoid printReverseList_stack(ListNode* pHead){    std::stack<ListNode*> nodes;    ListNode* pNode = pHead;    while (pNode != nullptr)    {        nodes.push(pNode);    pNode = pNode->mpNext;    }    while (!nodes.empty())    {        pNode = nodes.top();    std::cout << pNode->mVal << "\t";    nodes.pop();    }}#endifbool findVal(ListNode** pHead, int val){    ListNode* pNode = *pHead;    while(pNode != nullptr && pNode->mVal != val)    {        pNode = pNode->mpNext;    }    return pNode == nullptr ? false : true;}/**作用: 删除指定元素为val的节点*@pHead 指向头指针*@val 指定元素为val*/void removeNode(ListNode**pHead, int val) {    if (*pHead == nullptr)        return;    //将要被删除的节点    ListNode* pToBeDeleted = nullptr;    //若删除的节点是头节点    if ((*pHead)->mVal == val)    {        pToBeDeleted = *pHead;        *pHead = nullptr;    }    else    {        ListNode* pNode = *pHead;    //查找要删除的元素，while结束时返回要查找节点的前一个节点    while (pNode->mpNext != nullptr && pNode->mpNext->mVal != val)    {        pNode = pNode->mpNext;    }        //找到要删除的节点    if (pNode->mpNext != nullptr && pNode->mpNext->mVal == val)    {        pToBeDeleted = pNode->mpNext;        //指向要删除节点的下一个节点        pNode->mpNext = pNode->mpNext->mpNext;    }    }    if (pToBeDeleted != nullptr)    {        delete pToBeDeleted;    pToBeDeleted = nullptr;    }}int main(int argc, char* argv[]){    ListNode* pHead = nullptr;    int val;    //val == 0为结束标志    while (std::cin >> val && val != 0)        addNodeToTail(&pHead,  val);    std::cout << "打印初始化链表：";    printList(&pHead);#if USE_STACK    printReverseList_stack(pHead);#endif /*    std::cout << "\n反序打印链表： ";    printReverseList(pHead);    std::cout << "\n";    printList(&pHead);    std::cout << std::endl;*//*    std::cout << "\n请输入要查找的元素: ";    int find_val;    while (std::cin >> find_val && find_val != 0)    {        if (findVal(&pHead, find_val))        std::cout << "存在该元素" << std::endl;    else       std::cout << "不存在该元素" << std::endl;        std::cout << "请输入要查找的元素: ";    }    std::cout << "\n请输入要删除的节点： ";    int remove_val;    while (std::cin >> remove_val && remove_val != 0)    {        removeNode(&pHead, remove_val);    std::cout << "删除后的节点序列为 : " << std::endl;        printList(&pHead);        std::cout << "\n请输入要删除的节点： ";    }    */    //释放申请的内存空间    destroyList(&pHead);    return 0;}