Command terminated by signal 11 - c

Question

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
struct node{
char data;
int p;
struct node *ptr;
};
struct node *start=NULL;
struct node *insert()
{
struct node *new_node,*z;
int num;
char s;
printf("\nEnter -1 to stop.");
printf("\nEnter the characters and their priorities: ");
scanf("\n%c %d",&s,&num);
while(num!=-1)
{
new_node=(struct node *)malloc(sizeof(struct node));
new_node->data=s;
new_node->p=num;
if(start==NULL)
{
start=new_node;
z=start;
new_node->ptr=NULL;
}
else
{
z->ptr=new_node;
new_node->ptr=NULL;
z=z->ptr;
}
scanf("%c %d",&s,&num);
}
return start;
}
struct node *display()
{
struct node *z;
z=start;
printf("\nDisplaying elements:\n");
while(z!=NULL)
{
printf("\t%c [Priority=%d]\n",z->data,z->p);
z=z->ptr;
}
return start;
}
struct node *sortit()
{
struct node *z,*q;
int t;
char x;
z=start;
while(z->ptr!=NULL)
{
q=z->ptr;
while(q!=NULL)
{
if(z->p>q->p)
{
t=z->p;
x=z->data;
z->p=q->p;
z->data=q->data;
q->p=t;
q->data=x;
}
q=q->ptr;
}
z=z->ptr;
}
return start;
}
struct node *new_insert()
{
struct node *y,*z;
int n;
char s;
y=(struct node *)malloc(sizeof(struct node));
printf("\nEnter character and priority for new node:");
scanf("%c %d",&s,&n);
printf("%c",s);
y->data=s;
y->p=n;
printf("%c",y->data);
printf("%d",y->p);
if(n<start->p)
{
y->ptr=start;
start=y;
printf("%d",y->p);
}
else
{printf("\nff");
z=start;
while(z->ptr->p<=n&&z->ptr!=NULL)
z=z->ptr;
y->ptr=z->ptr;
z->ptr=y;
}
return start;
}
int main()
{
insert();
display();
sortit();
display();
new_insert();
display();
return 0;
}
In this C code, I have tried to implement priority queues.
Everything works perfectly fine except the new_insert() function. The print statements after y->p=n; in new_insert() function print 0.
Hence, the function doesn't work properly. Also, in display() function the print statement prints the [Priority] twice.
Hence, I am not able to add an external node in my priority queue.

Answer 1

Well, you code is not far from working I think.
There are some problems that can be corrected:
the scanf usage is problematic
%c selector must be use with caution, use " %c %d" to prevent end of line problems
return value must be checked
in function insert, z may not be initialized (if insert() is called when start is not NULL)
You don't need to cast malloc returned value.
I tested the following code with this input:
a 2
b 3
c 1
d -1
e 0
And I got this result:
Enter -1 to stop.
Enter the characters and their priorities:
Displaying elements:
a [Priority=2]
b [Priority=3]
c [Priority=1]
Displaying elements:
c [Priority=1]
a [Priority=2]
b [Priority=3]
Enter character and priority for new node:
s: 'e' n: '0'
e00
Displaying elements:
e [Priority=0]
c [Priority=1]
a [Priority=2]
b [Priority=3]
Seems to work isn't? You can test it online
And here's the corrected code:
#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
struct node{
char data;
int p;
struct node *ptr;
};
struct node *start=NULL;
struct node *insert()
{
/* initialize z in case of start is not null */
struct node *new_node,*z = start;
int num, ok;
char s;
printf("\nEnter -1 to stop.");
printf("\nEnter the characters and their priorities: ");
/* read the scanf return value */
ok = scanf(" %c %d",&s,&num);
/* and assert two elements have been read*/
while(ok == 2 && num!=-1)
{
new_node=malloc(sizeof(struct node));
new_node->data=s;
new_node->p=num;
if(start==NULL)
{
start=new_node;
z=start;
new_node->ptr=NULL;
}
else
{
z->ptr=new_node;
new_node->ptr=NULL;
z=z->ptr;
}
ok = scanf(" %c %d",&s,&num);
}
return start;
}
struct node *display()
{
struct node *z;
z=start;
printf("\nDisplaying elements:\n");
while(z!=NULL)
{
printf("\t%c [Priority=%d]\n",z->data,z->p);
z=z->ptr;
}
return start;
}
struct node *sortit()
{
struct node *z,*q;
int t;
char x;
z=start;
while(z->ptr!=NULL)
{
q=z->ptr;
while(q!=NULL)
{
if(z->p>q->p)
{
t=z->p;
x=z->data;
z->p=q->p;
z->data=q->data;
q->p=t;
q->data=x;
}
q=q->ptr;
}
z=z->ptr;
}
return start;
}
struct node *new_insert()
{
struct node *y,*z;
int n, ok;
char s;
printf("\nEnter character and priority for new node:");
ok = scanf(" %c %d",&s,&n);
if (2 == ok)
{
/* alloc y after having check that user gave usage stuff */
y = malloc(sizeof(struct node));
y->data=s;
y->p=n;
printf("%c",y->data);
printf("%d",y->p);
if(n<start->p)
{
y->ptr=start;
start=y;
printf("%d",y->p);
}
else
{
printf("\nff");
z=start;
while(z->ptr->p<=n&&z->ptr!=NULL)
z=z->ptr;
y->ptr=z->ptr;
z->ptr=y;
}
}
return start;
}
int main()
{
insert();
display();
sortit();
display();
new_insert();
display();
return 0;
}