编写算法逆置一个带头结点的双链表代码c++

以下是逆置一个带头结点的双链表的C++代码：

#include <iostream>

using namespace std;

struct ListNode {
    int val;
    ListNode* next;
    ListNode* prev;
    ListNode(int x) : val(x), next(NULL), prev(NULL) {}
};

ListNode* reverseList(ListNode* head) {
    if (head == NULL || head->next == NULL) {
        return head;
    }
    
    ListNode* curr = head->next;
    ListNode* prev = NULL;
    
    while (curr != NULL) {
        ListNode* next = curr->next;
        curr->next = prev;
        curr->prev = next;
        prev = curr;
        curr = next;
    }
    
    head->next = prev;
    head->next->prev = NULL;
    
    return head;
}

int main() {
    ListNode* head = new ListNode(-1);
    ListNode* tail = head;
    for (int i = 1; i <= 5; i++) {
        ListNode* node = new ListNode(i);
        tail->next = node;
        node->prev = tail;
        tail = node;
    }
    
    cout << "Original list: ";
    ListNode* curr = head->next;
    while (curr != NULL) {
        cout << curr->val << " ";
        curr = curr->next;
    }
    cout << endl;
    
    head = reverseList(head);
    
    cout << "Reversed list: ";
    curr = head->next;
    while (curr != NULL) {
        cout << curr->val << " ";
        curr = curr->next;
    }
    cout << endl;
    
    return 0;
}

这里使用了双指针法，通过一个 `prev` 指针和一个 `curr` 指针来逆置链表。同时需要注意一些细节，比如链表头结点的处理和指针的赋值顺序等。