显示一个排序的链表，其中包含 c 中的每个新元素

Question

所以我试图用 c 编写一个程序，让用户输入数字，直到输入数字 0。然后创建一个链表，将输入的整数从小到大排序。这是我的代码：

#include <stdio.h>
#include <stdlib.h>

typedef struct node{
    int data;
    struct node *ptr;
} node;

node* insert(node* head, int num) {
    node *temp, *prev, *next;
    temp = (node*)malloc(sizeof(node));
    temp->data = num;
    temp->ptr = NULL;
    if(!head){
        head=temp;
    } else{
        prev = NULL;
        next = head;
        while(next && next->data<=num){
            prev = next;
            next = next->ptr;
        }
        if(!next){
            prev->ptr = temp;
        } else{
            if(prev) {
                temp->ptr = prev->ptr;
                prev-> ptr = temp;
            } else {
                temp->ptr = head;
                head = temp;
            }
        }
    }
    return head;
}

void free_list(node *head) {
    node *prev = head;
    node *cur = head;
    while(cur) {
        prev = cur;
        cur = prev->ptr;
        free(prev);
    }
}

int main(){
    int num;
    node *head, *p;
    head = NULL;

    do {
        printf("Enter a number: ");
        scanf("%d",&num);
        printf("%d->\n", num);
        if(num) {
            head = insert(head, num);
        }
    } while(num);

    p = head;
    printf("\nThe entered numbers are:\n");

    while(p) {
        printf("%d->", p->data);
        p = p->ptr;
    }
    free_list(head);
    printf("NULL");

    return 0;
}

如您所见，输出将如下所示：

Enter number: 6
6->NULL
Enter number: 3
3->NULL
Enter number: 9
9->NULL
Enter number: 0
0->

The entered numbers are :
3->6->9->NULL

但是，我想要的是这些数字在输入和插入列表时进行排序（我还需要不显示 0）。所以输出应该是这样的：

Enter number: 6
6->NULL
Enter number: 3
3->6->NULL
Enter number: 9
3->6->9->NULL
Enter number: 0

The entered numbers are :
3->6->9->NULL

有人可以帮我解决这个问题吗？？？

Answer 1

您实际上是按排序顺序将元素插入到列表中。您只是在读入当前值而不是整个列表后打印当前值。

因此将打印代码放在一个函数中，然后在插入一个值并读取所有值后调用该函数。

Answer 2

我已经修改了一些你的代码，请检查：

#include <stdio.h>
#include <stdlib.h>

typedef struct node
{
  int data;
  struct node *ptr;
} node;

node *
insert (node * head, int num)
{
  node *temp, *prev, *next;
  temp = (node *) malloc (sizeof (node));
  temp->data = num;
  temp->ptr = NULL;
  if (!head)
    {
      head = temp;
    }
  else
    {
      prev = NULL;
      next = head;
      while (next && next->data <= num)
    {
      prev = next;
      next = next->ptr;
    }
      if (!next)
    {
      prev->ptr = temp;
    }
      else
    {
      if (prev)
        {
          temp->ptr = prev->ptr;
          prev->ptr = temp;
        }
      else
        {
          temp->ptr = head;
          head = temp;
        }
    }
    }
  return head;
}

void
free_list (node * head)
{
  node *prev = head;
  node *cur = head;
  while (cur)
    {
      prev = cur;
      cur = prev->ptr;
      free (prev);
    }
}

int
main ()
{
  int num;
  node *head, *p;
  head = NULL;

  do
    {
      printf ("\nEnter a number: ");
      scanf ("%d", &num);
      if (num != 0)
    {
      printf ("%d->\n", num);
    }
      if (num)
    {
      head = insert (head, num);
      p = head;
      printf ("\nThe entered numbers are:\n");

      while (p)
        {
          printf ("%d->", p->data);

          p = p->ptr;
        }
    }
    }
  while (num);


  free_list (head);

  return 0;
}

output->
Enter a number: 8
8->

The entered numbers are:
8->
Enter a number: 2
2->

The entered numbers are:
2->8->
Enter a number: 4
4->

The entered numbers are:
2->4->8->
Enter a number: 1
1->

The entered numbers are:
1->2->4->8->
Enter a number: 0

Answer 3

我不明白你是如何得到这个输出的

Enter number: 6
6->NULL
Enter number: 3
3->NULL
Enter number: 9
9->NULL
Enter number: 0
0->

在此 do-while 循环中

do {
    printf("Enter a number: ");
    scanf("%d",&num);
    printf("%d->\n", num);
    if(num) {
        head = insert(head, num);
    }
} while(num);

唯一输出内容的语句是

    printf("%d->\n", num);

但它不输出字符串 ->NULL.

函数 insert 中没有输出语句。

要在 do while 语句中获得所需的输出，您需要编写

do {
    printf("Enter a number: ");
    scanf("%d",&num);
    if(num) {
        head = insert(head, num);
        for ( p = head; p != NULL; p = p->ptr )
        {
            printf("%d->", p->data);
        }
        puts( "NULL " );   
    }
} while(num);

你的函数 insert 也太复杂了。 if 语句和局部变量太多。该函数可以写得更简单。例如

node * insert( node *head, int num ) 
{
    node *temp = malloc( sizeof( node ) );
    temp->data = num;

    if ( head == NULL || head->data < num )
    {
        temp->ptr = head;
        head = temp;
    }
    else
    {
        node *current = head;
        while ( ( current->ptr != NULL ) && 
                !( num < current->ptr->data ) )
        {
            current = current->ptr;
        }
        
        temp-ptr = current->ptr;
        current->ptr = temp;
    }

    return head;
}

显示一个排序的链表，其中包含 c 中的每个新元素

display a sorted linked list with every new element in c

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singly-linked-list