c++ - 将数组元素添加到链表中

Question

我有数组元素ar1[i]我想将该数组的数据添加到链表中

struct node
{
  int data;
  struct node*next;
};


void create(struct node *head,int ar1[] int i1)
{
struct node *temp, *p, *q;
int i;


head = (struct node*)malloc(sizeof(struct node));
temp = (struct node*)malloc(sizeof(struct node));


for (i=0; i<i1; i++) //lets say i1 is no. of data in array
{
    if(head == NULL)
    {
        head->data = ar1[i];
        head->next = NULL;
    }
    else
    {
        temp->data = ar1[i];
        temp->next = NULL;

        p = head;
        while(p->next != NULL)
            p = p->next;
        p->next = temp;
    }

}

我做了这个程序，但它不起作用。它接受输入数据，但不显示输出，也不终止程序。

编辑:正如每个人在评论中建议的那样，我尽了最大努力并提出了解决方案。实际上我的程序是从用户那里获取最多10位数字并对其进行算术运算。

这是我的代码:

   /*
     WAP to store at most 10 digit integer in a Singly linked list and 
     perform
      arithmetic operations on it.
   */

   #include<iostream>
   using namespace std;

   struct node
   {
     int data;
    struct node*next;
   };

void create(struct node *head,int ar1[],int ar2[], int i1, int i2)
{
struct node *newNode, *temp;
int i=0;

head = (struct node *)malloc(sizeof(struct node));

if(head == NULL)
{
    cout<<"Unable to allocate memory.";
}
else
{

    head->data = ar1[i]; // Link the data field with data
    head->next = NULL; // Link the address field to NULL

    temp = head;

    for(i=1; i<i1; i++)     //Create n nodes and adds to linked list
    {
        newNode = (struct node *)malloc(sizeof(struct node));

        if(newNode == NULL)     

        {
            cout<<"Unable to allocate memory.";
            break;
        }
        else
        {


            newNode->data = ar1[i]; 
            newNode->next = NULL;

            temp->next = newNode; 
            temp = temp->next; 
        }
    }
}

temp = head;

while(temp!=NULL)
{
    cout<<temp->data<<" ";
    temp= temp->next;
}   

}

int main()
{
struct node*head = NULL ;
int n1,n2;
int i1,i2,choice;
int ar1[10],ar2[10];

head = (struct node*)malloc(sizeof(struct node));

cout<<"Enter numbers you want to perform operations on\n1). ";
cin>>n1;
cout<<"2). ";
cin>>n2;

i1=0; i2=0;

while(n1)       //getting each digit of given number
{

    ar1[i1] = n1 %10;
    n1 /= 10;
    i1= i1 + 1;     
}

while(n2)       //getting each digit of given number
{

    ar2[i2] = n2 % 10;
    n2 /= 10;
    i2++;   
}

cout<<"\nChoose what operation you want to 
 perform:\n1.Addition\n2Subtraction\n";
cin>>choice;

create(head,ar1,ar2,i1,i2);
/*if(choice == 1)  I comment out this part i.e. not important rn.
{
    add(ar1,ar2);
}
else if (choice == 2)
    sub();
else
{
    cout<<"Please chose valid data\n";
}
*/
return 0;
}

Answer 1

有很多问题。您的 create 函数的整个逻辑是错误的:

void create(struct node *head, int ar1[], int i1)
{
  struct node *temp, *p, *q;
  int i;

  head = (struct node*)malloc(sizeof(struct node));  // Problem 1
  temp = (struct node*)malloc(sizeof(struct node));

  for (i = 0; i < i1; i++)
  {
    if (head == NULL)                                // Problem 2
    {
      head->data = ar1[i];  
      head->next = NULL;
    }
    else
    {
      temp->data = ar1[i];
      temp->next = NULL;

      p = head;
      while (p->next != NULL)
        p = p->next;

      p->next = temp;                                // Problem 3
    }
  }
}


...
create(myhead, myarray, maysize);                    // Problem 4
...

问题1

你分配内存太早了，你应该只在真正需要的时候分配它。

问题2

部分是由问题 1 引起的:这里 head 不能为 NULL (假设 malloc 没有失败，但那是另一个故事了)，因为你之前已将其分配给非 NULL 值。

问题3

这里 p->next 始终为 NULL，因为上面有 while 循环。

问题4

假设你不能像这样创建:

...
myhead = NULL;
...
create(myhead, myarray, maysize);

调用 create 后，

myhead 仍将为 NULL，您应该阅读 this SO article .