30 Day Challenge Day 6 | Hackerrank: Reverse a doubly linked list

题解

与Leetcode上翻转链表（206. Reverse Linked List）思路一致，只不过多了一个“prev”前节点的处理，这种题通过画图比较容易验证。

DoublyLinkedListNode* reverse(DoublyLinkedListNode* head) {
    if(!head || !head->next) return head;

    DoublyLinkedListNode* prev = nullptr;
    DoublyLinkedListNode* curr = head;

    while(curr) {
        DoublyLinkedListNode* temp = curr->next;
        curr->next = prev;
        curr->prev = temp;
        prev = curr;
        curr = temp;
    }

    return prev;
}