思考

常规想法遍历一遍单链表，记录长度再一次遍历，输出中间元素这样的效率不是最优另一种方式（来源于网络）search的速度是mid的两倍，search走完恰好mid走一半voidprintInt(intList*head){intList*mid,*search;//search的速度是mid的两倍，search走完恰好mid走一半mid=search=head;//保证midsearch启点一样while(search->next!=NULL){search=search->next;//search取下一个if(search->next!=NULL){search=search->next;//search再去下一个mid=mid->next;//mid就取一次}else{mid=mid->next;//search取到头，mid再往下取一位}}printf("\n%d",mid->num);}完整代码随机生成任意长度单链表输出单链表值输出位于中间的值奇数个是最中间值，偶数个是中间两个的前一个#include<stdio.h>#include<stdlib.h>#include<time.h>typedefstructIntList{intnum;structintList*next;}intList;intList*applyList();//生成随机长度单链表voidprintList(intList*head);//查看单链表voidprintInt(intList*head);//输出单链表中间值intList*applyList(){srand((unsigned)time(NULL));intlen=rand()%10+10;//10到20的随机数intList*head=(intList*)malloc(sizeof(intList));if(head==NULL)exit(-1);//链表头部申请失败head->next=NULL;while(len){intList*node=(intList*)malloc(sizeof(intList));node->num=rand()%10+20;node->next=head->next;head->next=node;len--;}returnhead;}voidprintList(intList*head){intList*t=head->next;while(t){printf("%d",t->num);t=t->next;}};voidprintInt(intList*head){intList*mid,*search;//search的速度是mid的两倍，search走完恰好mid走一半mid=search=head;//保证midsearch启点一样while(search->next!=NULL){search=search->next;//search取下一个if(search->next!=NULL){search=search->next;//search再去下一个mid=mid->next;//mid就取一次}else{mid=mid->next;//search取到头，mid再往下取一位}}printf("\n%d",mid->num);}intmain(){intList*list=applyList();//随机生成单链表printList(list);//查看链表的值printInt(list);//输出中间值return0;}