单链表的翻转

单链表的翻转

// 链表定义
struct SingleLinkedList {
    int value;
    struct SingleLinkedList *next;
};

// 打印链表中的数据
void printAllNodes(struct SingleLinkedList *head) {
    printf("%d \t", head->value);
    if (head->next == NULL) {
        return;
    }
    printAllNodes(head->next);
}

// 翻转单向链表
struct SingleLinkedList * reverseLinkedList(struct SingleLinkedList *head) {
    if (head == NULL) {
        return head;
    }
    if (head->next == NULL) {
        return head->next;
    }
    struct SingleLinkedList *preNode = NULL;
    struct SingleLinkedList *nextNode = NULL;
    while (head != NULL) {
        // 1.把前面的一个节点给下一个
        // 获取后继节点
        nextNode = head->next;
        // 新的后继节点指向前驱节点，实现翻转
        head->next = preNode;
        
        // 2.将当前节点向后移动
        preNode = head;
        head = nextNode;
    }
    return preNode;
}

测试

struct SingleLinkedList *linkedRoot = (struct SingleLinkedList *)malloc(sizeof(struct SingleLinkedList));
    linkedRoot->value = 100;
    linkedRoot->next = (struct SingleLinkedList *)malloc(sizeof(struct SingleLinkedList));
    linkedRoot->next->value = 99;
    linkedRoot->next->next = (struct SingleLinkedList *)malloc(sizeof(struct SingleLinkedList));
    linkedRoot->next->next->value = 98;
    linkedRoot->next->next->next = (struct SingleLinkedList *)malloc(sizeof(struct SingleLinkedList));
    linkedRoot->next->next->next->value = 97;

    printf("翻转前：\t");
    printAllNodes(linkedRoot);

    printf("\r\n翻转后：\t");
    struct SingleLinkedList * reversedLinked = reverseLinkedList(linkedRoot);
    printAllNodes(reversedLinked);