双向链表

//双向链表
#include <stdio.h>
#include <stdlib.h>

#define OK 1
#define FALSE 0
#define TRUE 1
#define ERROR 0

typedef struct elem {
  int n;
}elem;//可自己定义元素种类

typedef struct splist {
  splist* prior;
  elem data;
  splist* nest;
}splist,*list;

//创建并初始化链表
int InitList(list &L) {
  L = (list)malloc(sizeof(splist));
  if (L == NULL) return ERROR;
  L->data.n = 0;
  L->prior = L;
  L->nest = L;
  return OK;
}

//创建并添加元素
int CreateList(list &L) {
  L = (list)malloc(sizeof(splist));
  if (L == NULL) return ERROR;
  L->nest = L;
  L->prior = L;
  int n = 0, m = 0;
  printf("请输入元素的个数：");
  scanf("%d", &n);
  list p, q = L->nest;
  while (n--) {
    p = (list)malloc(sizeof(splist));
    if (p == NULL) return ERROR;
    scanf("%d", &m);
    p->data.n = m;
    p->prior = q;
    p->nest = L;
    q->nest = p;
    q = p;
  }
  L->prior = q;
  return OK;
}

//添加一个结点
int AddList(list &L, int i, int n) {
  if (i <= 0) return FALSE;
  int j = 0;
  list p = L;
  while (j < i-1 ) {   //找到第i-1个元素
    if (j != 0 && p == L) return ERROR;//防止i越界
    p = p->nest;
    j++;
  }
  list q = (list)malloc(sizeof(splist));
  if (q == NULL) return ERROR;
  q->data.n = n;
  q->nest = p->nest;
  q->prior = p;
  p->nest->prior = q;
  p->nest = q;
  return OK;
}

//删除一个结点
int DeleteList(list &L, int i) {
  if (i <= 0) return ERROR;
  list p = L;
  int j = 0;
  while (j < i - 1 && p->nest != L) {
    p = p->nest;
    j++;
  }
  if (p->nest == L) return ERROR;
  list q = p->nest;
  p->nest = q->nest;
  q->nest->prior = p;
  free(q);
  return OK;
}

//求链表长度并返回元素个数
int LengthList(list &L) {
  list p = L;
  int i = 0;
  while (1) {
    if (p == L && i != 0) return i;
    i++;
  }
  return FALSE;
}

//判断链表是否为空
int EmptyList(list &L) {
  if (L->nest == L) return TRUE;
  return FALSE;
}

//找到第i个元素并存到e中
int SearchList(list &L, int i, elem* e) {
  list p = L;
  int j = 0;
  while (j < i - 1) {
    if (p == L && j != 0) return FALSE;
    j++;
    p = p->nest;
  }
  e->n = p->nest->data.n;
  return OK;
}

//清空链表
int ClearList(list &L) {
  list p = L->nest,q;
  while (p != L) {
    q = p->nest;
    p->prior->nest = p->nest;
    p->nest->prior = p->prior;
    free(p);
    p = q;
  }
  return OK;
}

//销毁链表
int DestoryList(list &L) {
  list p = L->nest, q;
  while (p != L) {
    q = p->nest;
    p->prior->nest = p->nest;
    p->nest->prior = p->prior;
    free(p);
    p = q;
  }
  free(L);
  return OK;
}

//将b连在a的后面并销毁b
int ContactList(list &a, list &b) {
  list e;
  while (b->nest != b) {
    e = b->nest;
    b->nest = e->nest;
    e->nest->prior = b;
    e->nest = a;
    e->prior = a->prior;
    a->prior->nest = e;
    a->prior = e;
  }
  free(b);
  return 0;
}

int main()
{
  return 0;
}