带头结点的单链表（ 冒泡排序 一次遍历求中间结点的值） 链表 就地反转 倒数第k个结点

#include <iostream>
using namespace std;

typedef struct student
{
int num;
struct student *next;
}node;

node  *create()
{//with head node
node *head,*p,*s;//head -->head    p-->end   s -->middle node
int num;
head = new node[sizeof(struct student)];
p=head;
cin>>num;
while(num!=-1)
{
s = new node[sizeof(struct student)];
s->num= num;
p->next = s;
p = s;
cin>>num;

}
p->next = NULL;

return head;
}

int print(node *l)//return the len of the linklist
{
node *p = l;
int count = 0;
p = p->next;
while(p)
{
cout<<p->num<<" ";
p= p->next;
count++;
}
cout<<endl;
return count;
}

int GetLen(node *l)
{
node *p = l;
int count = 0;
p = p->next;
while(p)
{
p= p->next;
count++;
}
return count;
}

node *sort(node *l)
{//sort AES
int len = GetLen(l);
node *head = l;
node *p;//move forward
int temp;

for(int i = 0;i<len-1;i++)
{
p = head->next;
for(int j = 0;j<len-i-1;j++)
{
if(p->num>p->next->num)
{
temp = p->num;
p->num = p->next->num;
p->next->num = temp;
}
p = p->next;

}
}
return head;
}

int GetCenterNode(node *l)
{//一次遍历求中间结点的值
node *p2 = l;//two step
node *p1 = l;//one step

while(1)
{
p2 = p2->next->next;
p1 = p1->next;
if(p2->next == NULL)//len %2 ==0
break;
if(p2->next->next == NULL)//len %2 == 1
{
p1 = p1->next;
break;
}

}
return p1->num;

}

int main()
{
node *StudentLink = create();
int len= GetLen(StudentLink);
cout<<"len="<<len<<endl;
node *Sorted_StudetLink = sort(StudentLink);// O(n) + O(n*n)

cout<<"After sorting ..."<<endl;
print(Sorted_StudetLink);

cout<<"the list's center node data is "<<GetCenterNode(StudentLink)<<endl;//O(n)

return 0;
}

ListNode* ReverseList(ListNode* pHead)
{
ListNode* pNode=pHead;//当前结点
ListNode* pPrev=NULL;//当前结点的前一个结点
while(pNode!=NULL)
{
ListNode* pNext=pNode->m_pNext;
pNode->m_pNext=pPrev;//当前结点指向前一个结点

pPrev=pNode;//pPrev和pNode往前移动。
pNode=pNext;//这里要使用前面保存下来的pNext，不能使用pNode->m_pNext
}
return pPrev;//返回反转链表头指针。
}

ListNode* KthNodeFromEnd(ListNode* pHead,int k)
{
if(pHead==NULL||k==0)
return NULL;

ListNode* pNode=pHead;//当前结点
ListNode* pKthNode=pHead;//

while(k-1>0)
{
if(pNode->m_pNext!=NULL)
{
pNode=pNode->m_pNext;//让pNode先走k-1步
--k;
}
else
return NULL;
}

while(pNode->m_pNext!=NULL)
{
pNode=pNode->m_pNext;
pKthNode=pKthNode->m_pNext;
}

return pKthNode;
}