从尾到头打印链表

题目：输入一个链表，从尾到头打印链表每个节点的值

思路：1.递归实现（递归在本质上就是一个栈结构）

　　　 2.vector + stack，遍历链表将元素放入栈中，当遍历完整个链表后，再从栈顶开始逐个取出节点的值，放入vector容器中。

注意：头节点需要先开辟出空间，不可以直接赋空

思路1

typedef struct Node
{
    int nCount;
    Node* pNext;
}List;

void Print_Reverse(List* pHead)
{
    if(pHead == NULL || pHead->pNext == NULL) return;
    pHead = pHead->pNext;
    Print(pHead);
    cout<<pHead->nCount<<" ";
}

int main()
{
    int n,num;
    List* pHead = (List*)malloc(sizeof(List));
    pHead->pNext = NULL;
    cin>>n;
    List* pTail = pHead;
    while(n--)
    {
        List* p = (List*)malloc(sizeof(List));
        cin>>num;
        p->nCount = num;
        p->pNext = NULL;
        pTail->pNext = p;
        pTail = p;
    }
    Print_Reverse(pHead);
}

 思路2

vector<int> printListFromTailToHead(ListNode* head) {
    stack<struct ListNode*> s;
    vector<int> arr;
    struct ListNode* pHead = head;
    while(pHead != NULL)
    {
        s.push(pHead);
        pHead = pHead->next;
    }
    while(!s.empty())
    {
        pHead = s.top();
        arr.push_back(pHead->val);
        s.pop();
    }
    return arr;
}