problem Stack implementaion using a linked list

Question

I was trying to implement stack with linked list implementation but seems to encounter 'segmentation error' . The code seems to compile and also run but when I actually enter the value of 'times' int variable in the stdin. The code shows segmentation error. The scanf also doesn't show the formatted string.

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#define NAME_MAX 40

struct NODE{
    char name[NAME_MAX];
    int regno;
    int age;
    struct NODE* next;
};

struct STACK{
    struct NODE *head;
    int size;  
};

void printStack(const struct STACK *stack);
bool pushStack(struct STACK *stack);
bool makeStack(struct STACK *stack, int data_count);
void cleanStack(struct STACK *stack);

int main(){
    struct STACK list = {NULL,0};
    int times = 0;
    scanf("How many data you want to enter: %d", &times);
    if(!makeStack(&list, times)){
        fprintf(stderr, "Stack wasn't created\n");
    }
    printStack(&list);
    cleanStack(&list);
    return 0;
}

void cleanStack(struct STACK *stack){
    struct NODE *trav = stack->head;
    while(trav!=NULL){
        struct NODE *temp = trav;
        trav = trav->next;
        temp = NULL;
    }
}

void printStack(const struct STACK *stack){
    struct NODE *trav = stack->head;
    for(int counter=1; stack!=NULL; trav=trav->next,++counter,++stack){
        printf("%d: %s %d %d",counter,trav->name,trav->regno, trav->age);
    }
}

bool makeStack(struct STACK *stack, int data_count){
    while(data_count--){
        if(!pushStack(stack)){
            return false;
        }
    }
    return true;
}

bool pushStack(struct STACK *stack){
    struct NODE *temp = malloc(sizeof(struct NODE));
    if(temp==NULL) return false;
    scanf("Input Name: %s", temp->name);
    scanf("Input RegNo: %d", &temp->regno);
    scanf("Input age: %d", &temp->age);
    temp->next = stack->head;
    stack->head = temp;
    ++stack->size;
    return true;
}

@Jonathon could also share me a link from where I can learn how to use debuggers in IDE or code editors please. — Karnik Kanojia
– Karnik Kanojia, Commented Mar 17, 2021 at 15:13
Does this answer your question? Error in stack with linked list implementation — MANA624
– MANA624, Commented Mar 17, 2021 at 15:47
@MANA624 yeh it does but I changed and appended the cleanStack function. I took advices from this too and modified the functions as you see above. Thank you for helping though — Karnik Kanojia
– Karnik Kanojia, Commented Mar 18, 2021 at 5:00

Andy Sukowski-Bang · Accepted Answer · 2021-03-17 16:24:44Z

0

There are a few things wrong with your implementation.

You have to first print to stdout using printf and then you can scan for an input using scanf.

printf("Number of data points: ");
scanf("%d", &times);

And in the printStack function, you need to traverse over the linked list with a while-loop.

void printStack(const struct STACK *stack)
{
    struct NODE *trav = stack->head;
    int counter = 1;
    while (trav != NULL) {
        printf("%d: %s %d %d\n", counter, trav->name, trav->regno, trav->age);
        trav = trav->next;
        counter++;
    }
}

And in cleanStack, I would free(temp) instead of setting it to NULL.

By the way... You don't need to, but you can allocate memory for struct Node *temp like this (In my opinion it looks nicer):

struct NODE *temp = malloc(sizeof *temp);

edited Mar 17, 2021 at 16:24

answered Mar 17, 2021 at 14:43

Andy Sukowski-Bang

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