Confusion about printing elements with double-while

Question

Here are two linked lists 'list1' and 'list2'.

Where list1 and list2 have two datas : data1, data2.

They have nodes below : (data1, data2)

• list1 : (1,1) - (2,2)
• list2 : (3,3) - (4,4) - (5,5)

(bracket denotes each node)

while (list2 != NULL)
    {
        while (list1 != NULL)
        {
            printf("list1 contains : %d, %f\n", list1->data1, list1->data2);
            list1 = list1->NextNode;
        }

        printf("list2 contains : %d, %f\n", list2->data1, list2->data1);
        list2 = list2->NextNode;
    }

At First, I expected output as :

list1, list1, list2, list1, list1, list2, list1, list1, list2  

(I mean a printing order)

But I got :

list1, list1, list2, list2, list2.

So my question is:

1. Why my expectation failed?

2. How should I change my code to make code works like my expectation?

Thanks

Answer 1

After the first execution of the inner while loop (its first and single iteration)

while (list2 != NULL)
    {
        while (list1 != NULL)
        {
            printf("list1 contains : %d, %f\n", list1->data1, list1->data2);
            list1 = list1->NextNode;
        }

        printf("list2 contains : %d, %f\n", list2->data1, list2->data1);
        list2 = list2->NextNode;
    }

the pointer list1 becomes equal to NULL. Then after execution the code after the inner while loop the pointer list2 is also equal to NULL. So the both while loops have only one iterations.

If you want to have the expected by you output like

list1, list1, list2, list1, list1, list2, list1, list1, list2 

then write for example. Let's assume that the type of an object of the list is Node

    while (list2 != NULL)
    {
        for ( Node *temp1 = list1; temp1 != NULL; temp1 = temp1->NextNode )
        {
            printf("list1 contains : %d, %f\n", temp1->data1, temp1->data2);
        }

        printf("list2 contains : %d, %f\n", list2->data1, list2->data1);
        list2 = list2->NextNode;
    }