单链表的创建，查找，删除，顺序打印，倒序打印（剑指offer）

#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>
#endif

struct 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 p
4000
rintReverseList(ListNode* pHead)
{
if (pHead != nullptr)
{
if (pHead->mpNext != nullptr)
{
printReverseList(pHead->mpNext);
}

std::cout << pHead->mVal << "\t";
}
}
#if USE_STACK
void 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();
}
}
#endif

bool 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;
}