CODEWITHSUNDEEP
cfunctionlinked-listargumentspolynomials
Kasun Jalitha
Kasun Jalitha

Reputation: 25

linked list program for polynomials exits without giving any output

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

struct node{
    int coff;
    int pow;
    struct node* next;
};

struct node* head1 = NULL;
struct node* head2 = NULL;

void insert(int c, int p, struct node* head){
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    struct node* temp = head;
    newnode->coff = c;
    newnode->pow = p;
    newnode->next = NULL;
    
    if(head == NULL){
        head = newnode;
    }else{
        while(temp->next != NULL){
            temp = temp->next;
        }
        temp->next = newnode;
    }
    
}

void display(struct node* h){
    struct node* temp;
    temp = h;
    while(temp != NULL){
        printf("%dx^%d ", temp->coff, temp->pow);
        temp = temp->next;
    }
    printf("\n");
}

int main(){
    
    insert(3,2,head1);
    insert(5,1,head1);
    insert(4,0,head1);

    insert(9,2,head2);
    insert(6,1,head2);
    insert(2,0,head2);

    display(head1);
    display(head2);
    
    return 0;
}

I have created node struct for my linked list. Then i have created two functions for insert and display polynomials. I have created head1 and head2 for store address of two different polynominals. And I want use that head1 and head2 as arguments in insert and display functions. then finally I wanna print both polynomials. But there is a bottleneck. When I execute my program it exits without giving any output.

My expected output is :

3x^2 5x^1 2x^0

9x^2 6x^1 4x^0

How can i solve this problem? Is there anything wrong with (struct node* head) arguments in the functions? Why this program exits without giving any output?

Thank you so much!

Upvotes: 0

Views: 97

Answers (2)

grizzlybears
grizzlybears

Reputation: 510

Take a look at void insert(int c, int p, struct node* head)

Because 'head' is passed by value (and all C parameters do so), caller of this function has no chance to get the 'inside modified' head. So, in your case, in main(), head1 is always NULL.

I modified a bit from your code, it seems works:) But don't forget to free all allocated nodes.

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

struct node{
    int coff;
    int pow;
    struct node* next;
};

struct node* head1 = NULL;
struct node* head2 = NULL;

struct node* insert(int c, int p, struct node* head){
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    struct node* temp = head;
    newnode->coff = c;
    newnode->pow = p;
    newnode->next = NULL;
    
    if(head == NULL){
        head = newnode;
    }else{
        while(temp->next != NULL){
            temp = temp->next;
        }
        temp->next = newnode;
    }
    
    return head;
}

void display(struct node* h){
    struct node* temp;
    temp = h;
    while(temp != NULL){
        printf("%dx^%d ", temp->coff, temp->pow);
        temp = temp->next;
    }
    printf("\n");
}

int main(){
    
    head1 = insert(3,2,head1);
    insert(5,1,head1);
    insert(4,0,head1);

    head2 = insert(9,2,head2);
    insert(6,1,head2);
    insert(2,0,head2);

    display(head1);
    display(head2);
    
    return 0;
}

Upvotes: 1

xavc
xavc

Reputation: 1295

Your line head = newnode; isn't actually changing head1 and head2 because the pointers themselves were passed by value. This results in head1 and head2 remaining NULL, and thus resulting in no output. You can fix this issue by passing a pointer to a pointer to the head node to insert. A quick modification to your code to implement this:

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

struct node{
    int coff;
    int pow;
    struct node* next;
};

struct node* head1 = NULL;
struct node* head2 = NULL;

void insert(int c, int p, struct node **head){
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    struct node* temp = *head;
    newnode->coff = c;
    newnode->pow = p;
    newnode->next = NULL;
    
    if(*head == NULL){
        *head = newnode;
    }else{
        while(temp->next != NULL){
            temp = temp->next;
        }
        temp->next = newnode;
    }
    
}

void display(struct node* h){
    struct node* temp;
    temp = h;
    while(temp != NULL){
        printf("%dx^%d ", temp->coff, temp->pow);
        temp = temp->next;
    }
    printf("\n");
}

int main(){
    
    insert(3, 2, &head1);
    insert(5, 1, &head1);
    insert(4, 0, &head1);

    insert(9, 2, &head2);
    insert(6, 1, &head2);
    insert(2, 0, &head2);

    display(head1);
    display(head2);
    
    return 0;
}

Upvotes: 2

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