c实现按访问频度非递增有序的带头节点的双向链表检索关键字

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问题描述：按访问频度非递增有序的带头节点的双向链表检索关键字为x的节点。对该访问频度计数，并维护该链表有序。若为找到，则插入该节点。所有节点频度初值在建表时都为零。

代码如下：

#include <stdio.h>#include <stdlib.h>typedef struct doublenode{char key;int freq;struct doublenode *pre,*next; } DoubleLinkNode,*DoubleLinkList;DoubleLinkList loc(DoubleLinkList head, char x){DoubleLinkList p,q;p = head->next;head->key = x;while(p->key != head->key) p = p->next;if(p == head) //找不到关键字的节点 。新建个节点插在头结点前面 {q = (DoubleLinkList)malloc(sizeof(DoubleLinkNode));q->key = x;q->freq = 0;q->next = p;q->pre = p->pre ;p->pre->next = q;p->pre = q;}else {q = p;q->freq++;head->freq = q->freq;// head指针的频度要修改，否则下面的while跳不出去 while(q->freq > p->pre->freq) p = p->pre;//找到当前q应该存放在的位置。p始终指向链表中比当前q频度小的最前面指针 if(p != q){//先断开q q->pre->next = q->next;q->next->pre = q->pre;//再把q挂到p前面 q->next = p;q->pre = p->pre;p->pre->next = q;p->pre = q;}} printf("\nfinally:");p = head->next;while(p != head){printf("(%c,%d)",p->key,p->freq);p = p->next;}return head;}DoubleLinkList createdoublelinklist(char c[],int r[],int n){DoubleLinkList head,p,q;int i;head = (DoubleLinkList)malloc(sizeof(DoubleLinkNode));head->next = head;head->pre = head;p = head->next;if(n>0){for(i = 0; i < n; i++){while(p->next != head) p = p->next;q = (DoubleLinkList)malloc(sizeof(DoubleLinkNode));q->key = c[i];q->freq = r[i];q->pre = p;q->next = p->next;p->next->pre = q;p->next = q;}}printf("original:");p = head->next;while(p != head){printf("(%c,%d)",p->key,p->freq);p = p->next;}return head;}int main(){DoubleLinkList head;char x,c[5]={'a','b','c','d','e'};int r[5] = {5,3,3,2,1};head = createdoublelinklist(c,r,5);loc(head,'a');loc(head,'f');loc(head,'c');return 0;}

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