单链表排序

在华为的oj上面看到一道题，单链表排序，一看比较简单就拿来做了，结果搞了半天还是没有调通，这类基础的问题还是挺费脑筋的，回家后又费了半天劲才搞定，题目要求是，一个单链表如果已经排好序或者排序出异常返回空，按输入标识确定排序规则，比如flag为0 为从小到大，flag为1为从大到小数据结构和函数原型如下：

struct ListNode 
{
int m_nKey;
ListNode * m_pNext;
};
ListNode * sortNodeList (ListNode * head, int flag)；

我实现了一下代码 ，变量名起的不是太好，不过总体验证能通过：

ListNode * sortNodeList (ListNode * head, int flag)
{
ListNode * returnNode = head;
bool adjust = false;
ListNode * currentNode = head;
ListNode * preNode = NULL;
while (currentNode != NULL)
{
ListNode * walkNode = currentNode->m_pNext;
ListNode * minNode = NULL;
ListNode * preMinNode = NULL;
ListNode * tmpPreMinNode = NULL;
int minKey = currentNode->m_nKey;
bool change = false;
while (walkNode != NULL)
{
if (minKey > walkNode->m_nKey && !flag)
{
minKey = walkNode->m_nKey;
preMinNode = tmpPreMinNode;
minNode = walkNode;
change = true;
adjust = true;
}

if (minKey < walkNode->m_nKey && flag)
{
minKey = walkNode->m_nKey;
preMinNode = tmpPreMinNode;
minNode = walkNode;
change = true;
adjust = true;
}
tmpPreMinNode = walkNode;
walkNode = walkNode->m_pNext;
}

if (!change)
{
preNode = currentNode;
currentNode = currentNode->m_pNext;
continue;
}

ListNode * tmpNode= currentNode->m_pNext;
currentNode->m_pNext = minNode->m_pNext;

if (preMinNode != NULL)
{
minNode->m_pNext = tmpNode;
preMinNode->m_pNext = currentNode;
}
else
{
minNode->m_pNext = currentNode;
}

if (preNode != NULL)
{
preNode->m_pNext = minNode;
}
else
{
returnNode = minNode;
}


preNode = minNode;
currentNode = minNode->m_pNext;
}
if (!adjust)
{
returnNode = NULL;
}
return returnNode;
}
int _tmain(int argc, _TCHAR* argv[])
{
ListNode NodeList[5];
NodeList[0].m_nKey = 1;
NodeList[0].m_pNext = &NodeList[1];


NodeList[1].m_nKey = 2;
NodeList[1].m_pNext = &NodeList[2];


NodeList[2].m_nKey = 3;
NodeList[2].m_pNext = &NodeList[3];


NodeList[3].m_nKey = 6;
NodeList[3].m_pNext = &NodeList[4];


NodeList[4].m_nKey = 5;
NodeList[4].m_pNext = NULL;


ListNode * head = sortNodeList (&NodeList[0], 0);


while (head != NULL)
{
std::cout << "\n" << head->m_nKey;
head = head->m_pNext;
}
system ("pause");
return 0;
}