Question

So I’ve got this code already: http://pastebin.com/3wuFNWGA

And I’ve got these typedefs in a .h file: http://pastebin.com/JTG9XHvW

I need my push function to add a node to my_stack by allocating memory for the node, storing the data (new element) in the node, and inserting the node at the top of the stack. The code runs but when I try to print the value in my_stack->top->data after pushing a new value onto the stack, it always prints zero and not the element I supposedly pushed onto the stack.

For the life of me, I can’t figure out why. I don’t think there’s a problem arising when I create the new node and store the value in data so I’m thinking there’s a problem when I try to make my_stack->top point to the most recently added node?

This is also my first post on Stack Overflow. I hope I did everything right.

Here’s the push function to push a value onto the stack:

void push( Stack *my_stack, int newElement ) {
    Node_s *newNode;
    newNode = (Node_s *) malloc(sizeof(Node_s));
    if( newNode == NULL ) {
            printf("Error: malloc failed in push\n");
            exit(EXIT_FAILURE);
    }
    newNode->data = newElement;
    newNode->next = my_stack->top;
    my_stack->top = newNode;
}

Answer 1

Your code will print zero for the size of the stack as you never increase that.

Also it prints 0 for the element because the type of the data field is declared as double but you print it with integer specificator.

Changing:

printf("The value at the top of the stack is %d\n", my_stack->top->data);

to

printf("The value at the top of the stack is %lf\n", my_stack->top->data);

Fixes this problem.