LeetCode 反转链表-C++

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

两种思路：

第一种：以头节点的方式新建一个链表；
第二种：改变自身指针的指向 preNode curNode nextNode

代码实例：

#include 
#include 
#include 

typedef struct NodeList
{
    int val;
    NodeList* next;
}NodeList;

void initList(NodeList* head)
{
    NodeList* newNode;
    NodeList* tailNode = head;

    for (int i = 1; i <= 5; i++) {
        newNode = (NodeList*)malloc(sizeof(NodeList));
        newNode->val = i;
        newNode->next = NULL;
        tailNode->next = newNode;
        tailNode = newNode;
    }
}

void myPrintList(NodeList* list)
{
    while(NULL != list)
    {
        printf("%d ", list->val);
        list = list->next;
    }
    printf("\n");
}

/// 第一种：以头节点的方式新建一个链表
void convertList1(NodeList* srcList, NodeList* dstList)
{
    NodeList* newNode;
    while(NULL != srcList)
    {
        newNode = (NodeList*)malloc(sizeof(NodeList));
        newNode->val = srcList->val;
        newNode->next = NULL;

        newNode->next = dstList->next;
        dstList->next = newNode;

        srcList = srcList->next;
    }
}
// 第二种：改变自身指针的指向 preNode curNode nextNode
void convertList2(NodeList* head)
{
    NodeList* curNode = head, *preNode, *nextNode;

    while(NULL != curNode)
    {
        nextNode = curNode->next; // 先保存后面的节点
        curNode->next = preNode;
        preNode = curNode;
        curNode = nextNode;
    }
    myPrintList(preNode);
}

int main(int argc, char** argv)
{
    NodeList* head = (NodeList*)malloc(sizeof(NodeList));
    initList(head);
    myPrintList(head->next);

    NodeList* convertHead = (NodeList*)malloc(sizeof(NodeList));
    convertList1(head->next, convertHead);
    myPrintList(convertHead->next);

    convertList2(head->next);

    return 0;
}

运行结果：

1 2 3 4 5 
5 4 3 2 1 
5 4 3 2 1