双向链表的排序，单向链表的反转，合并两个有序链表

1.　　采用的方案：冒泡排序

　　　和数组的冒泡排序的思想没有很大的区别。直接 看代码吧。

　　　定义一下数据结构：

typedef struct student
{
    int num;
    float score;
    struct student *pre;
    struct student *pnext;
}node,*Node;

　　　排序代码：

Node sortt(Node head)
{
    Node p=head,pn=head;
    for(int i=0;i<n-1;i++)
    {
        p=head->next;
        pn=p->next;//p和pn总是两个相邻的节点，且pn在p之后
        for(int j=0;j<n-i-1;j++)
        {
            if(p->score > pn->score)
            {
                if(pn->next==NULL)
                {
                    p->next=NULL;
                    pn->pre=p->pre;
                    p->pre->next=pn;
                    pn->nextt=p;
                    p->pre=pn;
                }
                else
                {
                    p->next=pn->next;
                    pn->pre=p->pre;
                    p->pre->next=pn;
                    pn->next->pre=p;
                    p->pre=pn;
                    pn->next=p;
                    //位置交换结束
                    pn=p->next;//位置交换结束之后进行指针偏移，pn指向p的下一个节点
                }
            }
            else
            {
                p=p->next;
                pn=pn->next;
            }
        }
    }
    return head;
}

 

void TwoWayBubbleSort(LinkList &L)
{
    int exchange = 1;//设标记
    LinkList head = L;//双向链表头，算法过程中是向下起泡的开始结点
    LinkList tail = NULL;//双向链表尾，算法过程中是向上起泡的开始结点
    while(exchange)
    {
        LinkList p = head->next;
        exchange = 0;
        while (p->next != tail)
        {
            if (p->data > p->next->data)
            {
                LinkList temp = p->next; exchange = 1;
                p->next = temp->next; 
                if(temp->next)temp->next->prior = p;
                temp->next = p; p->prior->next = temp;
                temp->prior = p->prior; p->prior = temp;
            }
            else p = p->next;
        }
        tail = p;
        p = tail->prior;
        while (exchange&&p->prior != head)
        {

            if (p->data < p->prior->data)
            {
                LinkList temp = p->prior; exchange = 1;
                p->prior = temp->prior; temp->prior->next = p;
                temp->prior = p; p->next->prior = temp;
                temp->next = p->next; p->next = temp;
            }
            else p = p->prior;
        }
            head = p;
    }
}

2.　　保证不断链，每遍历一下就变换链的方向

　　　定义数据结构：

struct ListNode {
     int val;
     ListNode *next;
     ListNode(int x) : val(x), next(NULL) {}
 };

　　　代码：

ListNode* reverseList(ListNode* head) {
        ListNode *ans=NULL;
        ListNode *pre=NULL;
        ListNode *temp=head;
        while(temp!=NULL)
        {
            ListNode *nextt=temp->next;
            if(nextt==NULL)
                ans=temp;
            temp->next=pre;
            pre=temp;
            temp=nextt;
        }
        return ans;
    }

 3.　　合并两个有序链表

　　　

/**
*Definition for singly-linked list
*/
class ListNode{
    int val;
    ListNode next;
 
    ListNode(int x){
        val = x;
    }
}
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) return l2;
        if (l2 == null) return l1;
 
        ListNode head = null;
        if (l1.val <= l2.val){
            head = l1;
            head.next = mergeTwoLists(l1.next, l2);
        } else {
            head = l2;
            head.next = mergeTwoLists(l1, l2.next);
        }
        return head;
}

 4.　　单链表的快排

struct Node 
{
    int key;
    Node* next;
    Node(int nKey, Node* pNext)
        : key(nKey)
        , next(pNext)
    {}
};
 
 
Node* GetPartion(Node* pBegin, Node* pEnd)
{
    int key = pBegin->key;
    Node* p = pBegin;
    Node* q = p->next;
 
    while(q != pEnd)
    {
        if(q->key < key)
        {
            p = p->next;
            swap(p->key,q->key);
        }
 
        q = q->next;
    }
    swap(p->key,pBegin->key);
    return p;
}
 
void QuickSort(Node* pBeign, Node* pEnd)
{
    if(pBeign != pEnd)
    {
        Node* partion = GetPartion(pBeign,pEnd);
        QuickSort(pBeign,partion);
        QuickSort(partion->next,pEnd);
    }
}