#include<iostream>
#include<malloc.h>
using namespace std;
typedef char ElemType;
typedef struct Lnode                //节点类型
{ElemType data;struct Lnode *next;
}LinkList;
void InitList(LinkList *&L)         //初始化链表
{L = (LinkList *)malloc(sizeof(LinkList));L->next = L;
}
void DestroyList(LinkList *&L)
{LinkList *p = L,*q = p->next;while(q != NULL){free(p);p = q;q = q->next;}free(p);
}
int ListEmpty(LinkList *L)
{return (L->next == L);
}
int ListLength(LinkList *L)    //返回链表长度
{LinkList *p = L;int i = 0;while(p->next != L){i++;p = p->next;}return i;
}
void DisplayList(LinkList *L)
{LinkList *p = L->next;while(p != L){cout << p->data <<" ";p = p->next;}cout << endl;
}
int GetElem(LinkList *L, int i ,ElemType &e)
{int j = 0;LinkList *p;if(L->next != L){if(i==1){e = L->next->data;return 1;}else{p = L->next;while(j<i-1&&p!=L){j++;p = p->next;}if(p==L)return 0;else{e = p->data;return 1;}}}elsereturn 0;
}int LocateElem(LinkList *L,ElemType e)
{LinkList *p = L->next;int n =1;while(p != L && p->data != e){p = p->next;n++;}if(p==L)return 0;elsereturn n;
}
int ListInsert(LinkList *&L,int i,ElemType e)
{int j = 0;LinkList *p = L,*s;if(p->next ==L || i==1){s = (LinkList *)malloc(sizeof(LinkList));s->data = e;s->next = p->next;p->next = s;return 1;}else{p = L->next;while(j<i-2 && p !=L){j++;p = p->next;}if(p == L)return 0;else{s = (LinkList *)malloc(sizeof(LinkList));s->data = e;s->next = p->next;p->next = s;return 1;}}
}
int ListDelete(LinkList *&L,int i,ElemType &e)
{int j = 0;LinkList *p = L, *q;if(L->next != L){if(i==1){q = L->next;L->next = q->next;free(q);return 1;}else{p = L->next;while(j<i-2&&p!=L){j++;p = p->next;}if(p==L)return 0;else{q = p->next;p->next = q->next;free(q);return 1;}}}elsereturn 0;
}int main()
{LinkList *L;ElemType e;cout << "(1)初始化链表L： \n";InitList(L);cout << "(2)插入法建立链表：\n";ListInsert(L,1,'a');ListInsert(L,2,'b');ListInsert(L,3,'c');ListInsert(L,4,'d');ListInsert(L,5,'e');cout << "(3)输出单链表L：";DisplayList(L);cout << "(4)单链表长度: ";cout << ListLength(L) <<endl;cout << "(5)单链表L是：" << (ListEmpty(L)?"空":"非空") <<endl;GetElem(L,3,e);cout << "(6)单链表L的第三个元素是：" <<  e << endl;cout << "(7)元素a的位置是：" << LocateElem(L,'a') <<endl;cout << "(8)在第四个位置插入元素f";ListInsert(L,4,'f');cout << "(9)输出链表L：";DisplayList(L);cout << "(10)删除第三个元素\n";ListDelete(L,3,e);cout << "(11)输出单链表L：";DisplayList(L);cout << "(12)释放单链表L：\n";DestroyList(L);
return 0;
}