【王道数据结构】【chapter2线性表】【P43t13】

设有一头指针为L的带有表头结点的非循环双向链表，其每个结点中除有prior（前驱指针），data（数据）和next（后继指针）域外，还有一个访问频度域freq。在链表被起用前，其值均初始化为零。每当在链表中进行一次Locate(L,x)运算时，令元素值为x的结点中freq域的值增1，并使此链表中结点保持按访问频度非增（递减）的顺序排列，同时最近访问的结点排在频度相同的结点的最后，以便使频繁访问的结点总是靠近表头。试编写符合上述要求的Locate(L,x)运算的算法，该运算为函数过程，返回找到结点的地址，类型为指针型。

#include <iostream>
#include <time.h>
#include <stdlib.h>
typedef  struct node{
    int data;
    node* next;
    node* prev;
    int freq;
}node,*list;

list Init()
{
    list head=(list) malloc(sizeof (node));
    head->next= nullptr;
    head->data=-1;
    head->freq=0;
    head->prev= nullptr;
    return head;
}

list Buynewnode(int x)
{
    list tmp=new node;
    tmp->next= nullptr;
    tmp->data=x;
    tmp->freq=0;
    tmp->prev= nullptr;
    return tmp;
}

list Locate(list head,int x)
{
    list pointer=head;
    while(pointer->next){
        if(pointer->next->data==x) break;
        else pointer=pointer->next;
    }
    if(pointer->next== nullptr) return nullptr;
    pointer->next->freq++;
    list tmp=pointer;
    while(tmp!=head&&tmp->freq<=pointer->next->freq) tmp=tmp->prev;
    if(tmp==pointer) return pointer->next;//如果已经是排好的就不要再交换了。
    list t1=pointer->next->next,t2=pointer->next,t3=tmp->next;
    pointer->next=t1;
    if(t1) t1->prev=pointer;
    tmp->next=t2;
    t2->prev=tmp;
    t2->next=t3,t3->prev=t2;
    return t2;
}
int main() {
    srand(time(nullptr));
    list head=Init();
    list pointer=head;
    printf("Initian\n");
    for(int i=0;i<10;i++)
    {
        pointer->next= Buynewnode(i+1);
        pointer->next->prev=pointer;
        pointer=pointer->next;
    }

    for(pointer=head->next;pointer!= nullptr;pointer=pointer->next) {
        printf("%3d",pointer->data);
    }
    puts("");
    printf("frequency\n");

    for(pointer=head->next;pointer!= nullptr;pointer=pointer->next) {
        printf("%3d",pointer->freq);
    }
    puts("");

    printf("Input\n");

    for(int i=0;i<100;i++)
    {
        int x=rand()%10+1;
        printf("%3d",x);
        Locate(head,x);
    }
    puts("");

    printf("order\n");

    for(pointer=head->next;pointer!= nullptr;pointer=pointer->next) {
        printf("%3d",pointer->data);
    }
    puts("");

    printf("frequency\n");
    for(pointer=head->next;pointer!= nullptr;pointer=pointer->next) {
        printf("%3d",pointer->freq);
    }
    puts("");
    return 0;
}