头插法建立链表--逆序输出

#include<stdio.h>

#include<malloc.h>

#include<stdlib.h>

#define OK 1;

#define ERROR -1;

typedef char elemdata;

typedef struct node {

elemdata data;

struct node *next;

}Lnode,*linklist; //单链表结点类型描述

//创建一个带头结点的单链表（头插法）

Lnode *headcreat()

{

Lnode *h,*p;

elemdata ch;

h = (Lnode*)malloc(sizeof(Lnode));

h->next = NULL;

while((ch = getchar()) != '\n')

{

p = (Lnode*)malloc(sizeof(Lnode));

  p->data = ch;

  p->next = h->next;

  h->next = p;

}

return (h);

}

//取元素

//读取单链表中第i个元素，1<=i<=length(h)

elemdata get(Lnode *h, int i)

{

int j = 1;

Lnode *p;

p = h->next;

while(p && j < i)//移动p，直到p为空，或者j < i

{

  p = p->next;

  j++;

}

if((p != NULL) && j == i)

  return (p->data);

else

  return ERROR;

}

//删除元素

//删除i元素，并返回其值，1<=i<=length(h)  

elemdata delete(Lnode *h, int i)

{

int j = 1;

elemdata e;

Lnode *p, *q;

p = h->next;

while((p->next != NULL)&& j < i-1)

{

  p = p->next;

  j++;

}

if((p->next != NULL) && j == i-1)

{

  q = p->next;

  p->next = q->next;

  e = q->data;

  free(q);

  return e;

}

else

  return ERROR;

}

//插入元素

//第i个元素之前插入一个元素

int insert(Lnode *h, int i, elemdata x)

{

Lnode *p, *s;

p = h->next;

int j = 1;

while(p && j < i - 1)//寻找第i－1个结点

{

  p = p->next;

  j++;

}

if(p && j == i- 1)

{

  s = (Lnode *)malloc(sizeof(Lnode));

  s->next = p->next;

  p->next = s;

  s->data = x;

  return OK;

}

else

  return ERROR;

}

//求链表的长度

int length(Lnode *h)

{

int i = 0;

Lnode *p;

p = h->next;

while(p != NULL)

{

  p = p->next;

  i++;

}

return i;

}

//查找链表中是否存在数据域为x的结点

//若存在返回该结点的指针，否则返回空。

elemdata locate(Lnode *h, elemdata x)

{

Lnode *p;

p = h->next;

while(p&&(p->data != x))

  p = p->next;

if(p)

  return p->data;

else

  return ERROR;

}

//主程序

#include"lklist_1.c"

int main()

{

Lnode* headlist, taillist;

int j = 1, count;

headlist = headcreat();

printf("请输入所创建链表的元素个数：");

scanf("%d", &count);

printf("取单链表中第2个元素：");

printf("%c\n",get(headlist, 2));

printf("删除单链表中第3个元素：");

printf("%c\n",delete(headlist, 3));

printf("在链表中第3个元素之前插入c.\n");

insert(headlist, 3, 'c');

printf("依次输出单链表中的元素：");

for(j = 1; j < count + 1; j++)

{

  printf("%c",get(headlist, j));

}

printf("\n");

printf("链表的长度为：%d\n", length(headlist));

printf("查找链表中是否存在数据域为x的结点：");

if(-1 == locate(headlist, 'x'))

  printf("链表中没有此元素。\n");

else

  printf("%c\n",locate(headlist, 'x'));

return 0;

}