while(q!=p) { pre=q;q=q->next; } pre->next=p->next; p->next=head; head=p; break;这段代码作用是啥啊

这段代码的作用是将链表中节点p移动到链表头部。具体实现是找到p的前一个节点pre和p的后一个节点q，然后将pre的next指向p的next，将p的next指向当前链表的head，再将head指向p，从而实现将节点p移动到链表头部的操作。

相关问题

#include <iostream> #include "listnode.h" using namespace std; struct listNode { listNode * prev, * next; int val; listNode(): val(0), prev(nullptr), next(nullptr){} listNode(int v, listNode *p, listNode *n): val(v), prev(p), next(n) { if (prev != nullptr) prev->next = this; if (next != nullptr) next->prev = this; } }; class OrderedList { protected: listNode * root; public: OrderedList(){root=new listNode();} ~OrderedList(){ listNode* cur=root; if(cur->prev!=nullptr)cur=cur->prev; if(cur!=nullptr){listNode*tmp=cur;cur=cur->next;delete tmp;}} virtual void insert(int val)=0; void printList() const { listNode* cur=root; if(cur->prev!=nullptr)cur=cur->prev; if(cur!=nullptr){cout<<cur->val<<' ';cur=cur->next;} } }; class AscendOrderedList:public OrderedList { public: AscendOrderedList(){root=new listNode();} ~AscendOrderedList(){ listNode* cur=root; if(cur->prev!=nullptr)cur=cur->prev; if(cur!=nullptr){listNode*tmp=cur;cur=cur->next;delete tmp;}} virtual void insert(int v){ listNode*pre=root; while(v>pre->val&&pre!=nullptr){pre=pre->next;} listNode*ins=new listNode(v, pre,pre->next); pre->next=ins; ins->next->prev=ins; } }; class DescendOrderedList:public OrderedList { public: DescendOrderedList(){root=new listNode();} ~DescendOrderedList(){ listNode* cur=root; if(cur->prev!=nullptr)cur=cur->prev; if(cur!=nullptr){listNode*tmp=cur;cur=cur->next;delete tmp;}} virtual void insert(int v){ listNode*pre=root; while(v<pre->val&&pre!=nullptr){pre=pre->next;} listNode*ins=new listNode(v, pre, pre->next); pre->next=ins; ins->next->prev=ins; } }为什么运行崩溃

这段代码中可能会有多个问题，具体原因需要根据您的输入、程序运行环境以及错误提示等来确定。以下是一些可能的问题和建议：

1. 在 `listNode` 的构造函数中，需要判断 `prev` 和 `next` 是否为空指针，才能为它们的 `prev` 和 `next` 成员变量赋值。修改代码如下：

listNode(int v, listNode* p, listNode* n) : val(v), prev(p), next(n) {
    if (prev != nullptr) {
        prev->next = this;
    }
    if (next != nullptr) {
        next->prev = this;
    }
}

2. 在 `OrderedList` 和其子类的析构函数中，需要循环删除链表中的所有节点。修改代码如下：

~OrderedList() {
    listNode* cur = root;
    while (cur->next != nullptr) {
        cur = cur->next;
        delete cur->prev;
    }
    delete cur;
}

~AscendOrderedList() {
    listNode* cur = root;
    while (cur->next != nullptr) {
        cur = cur->next;
        delete cur->prev;
    }
    delete cur;
}

~DescendOrderedList() {
    listNode* cur = root;
    while (cur->next != nullptr) {
        cur = cur->next;
        delete cur->prev;
    }
    delete cur;
}

3. 在 `AscendOrderedList` 和 `DescendOrderedList` 的 `insert()` 方法中，需要先判断当前节点是否为空指针，否则会出现访问空指针的错误。修改代码如下：

void insert(int v) {
    listNode* pre = root;
    while (pre->next != nullptr && v > pre->val) {
        pre = pre->next;
    }
    listNode* ins = new listNode(v, pre, pre->next);
    pre->next = ins;
    if (ins->next != nullptr) {
        ins->next->prev = ins;
    }
}

void insert(int v) {
    listNode* pre = root;
    while (pre->next != nullptr && v < pre->val) {
        pre = pre->next;
    }
    listNode* ins = new listNode(v, pre, pre->next);
    pre->next = ins;
    if (ins->next != nullptr) {
        ins->next->prev = ins;
    }
}

以上是可能的问题和建议，如果您还有其他问题或者需要更多帮助，请提供更多详细的信息和错误提示，以便我们更好地帮助您解决问题。

void deletes(LinkList *h,int min,int max) { LinkList *p = h->next, *q, *pre = h, *s; while(p&&p->data<=min) {//查找第一个大于min的结点 pre = p; p = p->next; } if(p) { while(p&&p->data<max) { //查找第一个大于max的结点 p = p->next; } q = pre->next; pre->next = p;//修改指针 while(q!=p) {//释放结点空间 s = q->next; free(q); q = s; } } }的时间复杂度和空间复杂度分析

!= NULL) { if(p->data >= min && p->data <= max) { q = p; pre->next = q->next; p = p->next; free(q); } else { pre = p; p = p->next; } } }

This function deletes all nodes in a linked list whose data values fall within a given range (min to max inclusive). It uses four pointers - p, q, pre, and s - to traverse the list and delete nodes as necessary.

The function takes in a pointer to the head node of the list as its first argument, and the minimum and maximum values for the range as its second and third arguments, respectively.

The while loop continues iterating through the list until p reaches the end (i.e., p == NULL). Inside the loop, the function checks whether the data value of the current node (p->data) falls within the given range. If it does, the node is deleted by setting q to point to the current node, updating the previous node's next pointer (pre->next) to skip over the current node, and freeing the memory used by the current node (using the standard library function free()).

If the current node's data value does not fall within the given range, the function simply updates pre and p to point to the next nodes in the list.

Once the loop finishes, all nodes whose data values fall within the given range should have been removed from the list.