将数组元素加入链表

Question

I have array elements ar1[i] i want to add the data of this array into linked list

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;
    }

}

I did this program but its not working. It is accepting input data but not showing output and neither terminating the program.

Edit : As everyone suggested in comments I tried my best and came up with solution. Actually my program was to get at most 10 digit number from user and perform Arithmetic operations on it.

Here is my code :

   /*
     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

There are many issues.The whole logic of your create function is wrong:

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
...

Problem 1

You allocate memory too early, you should allocate it only whe you really need it.

Problem 2

Partly induced by Problem 1: head cannot be NULL here (assuming malloc doesn't fail, but that's another story) because you've assigned it to a non NULL value just before.

Problem 3

Here p->next is always NULL because of the while loop just above.

Problem 4

Suppose you cann create likes this:

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

myhead will still be NULL after the call to create , you should read this SO article .

Answer 2

Just understand the logic by using paper and pencil , then sequentially optimize the code .

struct node
{
    int val;
    struct node *next;
};
struct node *head=NULL, *last=NULL;

void insert( int value)
{
    struct node *tmp;
    tmp=(struct node *)malloc(sizeof(struct node));
    tmp->val=value;
    tmp->next=NULL;
    if( head == NULL )
    {
        head=tmp;
        last=tmp;
    }
    else
    {
        last->next=tmp;
        last=tmp;
    }
}

void printlist()
{
    struct node *tmp=head;
    printf("The list is:");
    while( tmp != NULL )
    {
        printf(" %d", tmp->val);
        tmp=tmp->next;
    }
    printf("\n");
}
void search( )
{
    printf("Which value to Search?");
    int n, k=0;
    scanf("%d",&n);
    struct node *tmp=head;
    while( tmp != NULL )
    {
        if( tmp->val == n )
            k=1;
        tmp=tmp->next;
    }
    if( k )
        printf("Yes\n");
    else
        printf("No\n");
}
void deletenode( )
{
    int n, posi;
    printf("Where to Delete?\n");
    printf("1\tFirst Position\n");
    printf("2\tLast Position\n");
    printf("3\tAny Desired Position\n");
    scanf("%d",&n);
    if( n == 1 )
    {
        struct node *tmp=head;
        tmp=tmp->next;
        head=tmp;
        printlist();
    }
    else if( n == 2 )
    {
        struct node *tmp=head ;
        while( 1 )
        {
            if( tmp->next->next == NULL )
            {
                tmp->next=NULL;
                break;
            }
            else
                tmp=tmp->next;
        }
        printlist();
    }
    else if( n == 3 )
    {
        int i=1;
        printf("Enter Position: ");
        scanf("%d",&posi);
        struct node *tmp=head;
        while( tmp->next != NULL && i <= posi )
        {
            if( i+1 == posi )
            {
                tmp->next=tmp->next->next;
                break;
            }
            else
            {
                i++;
                tmp=tmp->next;
            }
        }
        printlist();
    }
}

void ins()
{
    int n, v, posi;
    printf("Where to insert?\n");
    printf("1\tFirst Position\n");
    printf("2\tLast Position\n");
    printf("3\tAny Desired Position\n");
    scanf("%d",&n);
    if( n == 1 )
    {
        printf("Enter value: ");
        scanf("%d",&v);
        struct node *tmp;
        tmp=(struct node *)malloc( sizeof(struct node));
        tmp->val=v;
        tmp->next=head;
        head=tmp;
        printlist();
    }
    else if( n == 2 )
    {
        printf("Enter value: ");
        scanf("%d",&v);
        struct node *tmp;
        tmp=(struct node *)malloc(sizeof(struct node));
        tmp->val=v;
        tmp->next=NULL;
        last->next=tmp;
        last=tmp;
        printlist();
    }
    else if(n == 3 )
    {
        int i=1;
        printf("Enter position: ");
        scanf("%d",&posi);
        printf("\nEnter value: ");
        scanf("%d",&n);
        struct node *tmp1, *tmp=head, *tmp2;
        tmp1=(struct node *)malloc(sizeof(struct node));
        tmp1->val=n;
        tmp1->next=NULL;
        while( tmp->next != NULL && i <= posi)
        {
            if( i+1 == posi )
            {
                tmp2=tmp->next;
                tmp->next=tmp1;
                tmp1->next=tmp2;
            }
            i++;
            tmp=tmp->next;
        }
        printlist();
    }
}
int main()
{
    int n;
    printf("Enter value & Enter -1 to exit.\n");
    while( 1 )
    {
        scanf("%d",&n);
        if( n < 0 )
            break;
        insert(n);
    }
    printlist();
    printf("Enter choice:\n\n");
    printf("1\tInsert\n");
    printf("2\tDelete\n");
    printf("3\tSearch\n");
    printf("4\tExit\n");
    scanf("%d",&n);
    if( n == 1 )
        ins();
    else if( n == 2 )
        deletenode();
    else if( n == 3 )
        search();
    else if( n == 4 )
        return 0;
    return 0;
}