adding new nodes to linked list

I have this code to sort a linked list which asks the user to add nodes to the lists till the user presses y or Y. But what is happening currently is that after insertion of one node the program moves ahead without waiting for the input from the user. Is it that i am doing something wrong when asking input from the user.

[insert]

Code:

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

struct node
{
        int data;
        struct node* link;
} *start;

void addatend(struct node**, int);
void display(struct node*);
int count(struct node*);
void selection_sort(int);
void bubble_sort(int);
void getdata();

int main(void)
{
        int n;

        getdata();
        display(start);
        n = count(start);

        selection_sort(n);
        display(start);
        n = count(start);

        getdata();
        display(start);
        n = count(start);

        bubble_sort(n);
        display(start);
        n = count(start);

        return 0;
}


void getdata()
{
        struct node *newnode;
        int val;
        char ch;
        newnode = NULL;

        do
        {
                printf("\nEnter the value");
                scanf("%d", &val);

                addatend(&newnode, val);

                printf("\nAny more nodes");
                ch = getchar();
        }while (ch == 'y' || ch == 'Y');
       
        start = newnode;
       
}


void addatend(struct node **q, int data)
{       

        struct node *temp;
        temp = *q;

        if(*q == NULL)
        {
                // adding the first node
                *q = malloc(sizeof(struct node));
                temp = *q;
        }

        else
        {
                // go to last node
                while(temp ->link != NULL)
                        temp = temp->link;

                temp->link = malloc(sizeof(struct node));
                temp = temp->link;
        }

        temp ->data = data;
        temp ->link = NULL;
}

void display (struct node *q){

        int i = 0;
        struct node *temp;

        temp = q;
        while (temp != NULL){
                printf("\nThe data at loc %d is %d", i , temp ->data);
                temp = temp->link;
                i++;
        }
}

int count (struct node *q){

        struct node *temp;
        int count = 0;

        temp = q;
        while (temp != NULL){
                ++count;
                temp = temp -> link;
        }

        printf("\nCount %d", count);
        return count;
}

void selection_sort(int n)
{
        int i,j,temp;
        struct node *p, *q;

        p = start;
        for(i = 0;i<n-1;i++)
        {
                for(j=i+1;j<n;j++)
                {
                        if(p->data > q->data)
                        {
                                temp = p->data;
                                p->data = q->data;
                                q->data = temp;
                        }
                        q = q->link;
                }
                p= p->link;
        }
}

void bubble_sort(int n)
{
        int i,j,k, temp;
        struct node *p,*q;

        for(i = 0;i<n-1;i++)
        {
                p = start;
                q = p->link;

                for(j=1;j<n;j++)
                {
                        if(p->data > q->data)
                        {
                                temp = p->data;
                                p->data = q->data;
                                q->data = temp;
                        }
                        p= p->link;
                        q= q->link;
                }
        }
}

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The FAQ should answer your question: Cprogramming.com FAQ > Flush the input buffer

Although I'd probably use fgets() instead.

Okay i tried but it does not work.

[insert]

Code:

---


        puts("Flushing input");
                while((ch = getchar()) != '\n' && ch != EOF);
       
                printf("\nAny more nodes");
                ch = fgets(buf, 1 , stdin);
        }while (ch == 'y' || ch == 'Y');

---

Control passes away from the getdata function to display and count in the main even when i have not finished entering the elements.

Why are you using fgets to read one character? That's weird.


Quzah.

fgets is supposed to read one line. But the thing is that i just want from the user one character y or Y and when i was using
ch = getchar();

the post above said it should not be used and use fgets instead :-(

Okay i figured out an alternative way of doing this

Using getche() or getch() instead of getchar().

Also noted that getchar() is not an interactive function for taking the input from the user as it buffers the input until enter is pressed.

Quote:

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@zacs7

Although I'd probably use fgets() instead.

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@zacs7

Can you please explain of using fgets for taking the input from the user which in this case is a single character? I really did not get your point of using fgets when i am to read a single character.

fgets doesn't return the first character read. Read your book or "man fgets". (And of course, the tutorial advised you to do fgets in place of all the stuff you had before it -- the scanf and the flushing of input -- not after it.)

Quote:

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Originally Posted by roaan

I have this code to sort a linked list which asks the user to add nodes to the lists till the user presses y or Y. But what is happening currently is that after insertion of one node the program moves ahead without waiting for the input from the user. Is it that i am doing something wrong when asking input from the user.

[insert]

Code:

---

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

struct node
{
        int data;
        struct node* link;
} *start;


void getdata()
{
        struct node *newnode;
        int val;
        char ch;
        newnode = NULL;

        do
        {
                printf("\nEnter the value");
                scanf("%d", &val);

                addatend(&newnode, val);

                printf("\nAny more nodes");
                ch = getchar();
        }while (ch == 'y' || ch == 'Y');
       
        start = newnode;
       
}

---

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Instead of getchar() in the colored line just use scanf() with a space after the first double quotes. That will eat up the \n stored in the buffer. This way you dont have to flush the buffer either.

You will get a segfault in your selection_sort. You should initialize q to something, perhaps like what you have done within your bubble_sort.