User defined Functions and Linked Lists in C

问题

I'm a bit stuck on how to make a user defined function that would printout the output. I also have to make a user defined function that will add up the data in each node and print out the total but it's not adding up correctly and the format is a little off as well.

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

char printout();
int sum();
typedef struct node
{
    int number;
    struct node*next;
} node;

char printout()
{

};
int sum()
{
    int s,sum_all=0, node_sum=0;
    for(s=0;s=100;s++)
    {
        sum_all=node_sum+s;
        return printf("The sum of all nodes is %d.\n",sum_all);
    };

};
int main()
{
    srand (time(NULL));
    int i, total=0;
    struct node*head=malloc(sizeof(struct node));
    head->number = rand()%100;
    printf("Node #%d contains %d.\n", 0, head->number);

    struct node*here=head;

    for (i=1; i<100; i++)
    {
        here->next=malloc(sizeof(struct node));
        here->number=rand()%100;
        printf("Node #%d contains %d.\n", i, here->number);
    };
    total=sum(here->number);
    printf("%2.2d", total);
    return 0;
}

回答1:

There is the litany of errors here, but let's just focus on the most important meat:

You should be pass the list's head to the function sum(), ie

sum(head); // This is how you call most linked list functions.

by which you should change the header to

int sum(struct node *head)
{ ... }

This is not an array. You should traverse the linked list correctly.

I can't show all the code for you, as this is what your professor wants you to learn.

But you should be using these

for( struct node*p = head; p!=NULL; p=p->next)

instead of these

for( s=0; s<=100; s++)

You also forgot to step forward in your malloc-and-fill-with-rand loop

here = here->next; // this does in linked lists what i++ does in arrays

and this

sum_all += p->number; // p->number is analogous to array[i]

instead of

sum_all = node_sum +s; // what are s and node_sum anyway?

Also, if you insist that sum return something, It should return, well, the sum;

return sum_all;

And don't print it inside the function

printf("The sum of all nodes is %d.\n",sum_all); // please don't

Because you're already printing it outside.

total = sum(head);
printf("%2.2d", total);

Please try to think first what your code is going to accomplish instead of putting code blankly. It will help you a lot. Good luck!

来源：https://stackoverflow.com/questions/43564342/user-defined-functions-and-linked-lists-in-c

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