Link List Problem

dstask4.c

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

struct Node {
    int data;
    struct Node *link;
};

void printList(struct Node *head) {
    struct Node *ptr = head;
    while(ptr != NULL) {
        printf("%d ", ptr->data);
        ptr = ptr->link;
    }
    printf("\n");
}

void add_beg(struct Node **head, int key) {
    struct Node *ptr = (struct Node *)malloc(sizeof(struct Node));
    ptr->data = key;
    ptr->link = *head;
    
    *head = ptr;
}

void add_end(struct Node **head, int key) {
    struct Node *ptr;
    ptr = (struct Node *)malloc(sizeof(struct Node));
    ptr->data = key;
    ptr->link = NULL;
    
    if(*head == NULL)
        *head = ptr;
    else {
        struct Node *lastNode = *head;
        
        while(lastNode->link != NULL) {
            lastNode = lastNode->link;
        }
        lastNode->link = ptr;
    }
}

int getpos(struct Node *head, int key) {
    int pos = 0;
    struct Node* ptr;
    ptr = head;
    while (ptr != NULL && ptr->data != key) {
        pos++;
        ptr = ptr->link;
    }
    return (ptr != NULL) ? pos : -1;
}

void addpos(struct Node *head, int key, int pos) {
    struct Node *ptr = head;
    struct Node *ptr2 = malloc(sizeof(struct Node));
    ptr2->data = key;
    ptr2->link = NULL;
    
    pos--;
    while(pos != 1) {
        ptr = ptr->link;
        pos--;
    }
    ptr2->link = ptr->link;
    ptr->link = ptr2;
}

void delpos(struct Node **head, int pos) {
    struct Node *current = *head;
    struct Node *previous = *head;
    if (*head == NULL)
        return;
    else if(pos == 1) {
        *head = current->link;
        free(current);
        current = NULL;
    }
    else {
        while(pos != 1) {
            previous = current;
            current = current->link;
            pos--;
        }
        previous->link = current->link;
        free(current);
        current = NULL;
    }
}

struct Node* reverse(struct Node *head) {
    struct Node *prev = NULL;
    struct Node *next = NULL;
    while(head != NULL) {
        next = head->link;
        head->link = prev;
        prev = head;
        head = next;
    }
    head = prev;
    return head;
}
int main() {
    struct Node* head = (struct Node*)malloc(sizeof(struct Node));
    head = NULL;

    int i;
    int n;
    scanf("%d", &n);
    if(n >= 2 && n <= 600) {
    for(i = 0; i < n; i++) {
        int l;
        scanf("%d", &l);
        
        if(l == 1) {
            int x;
            scanf("%d", &x);
            add_end(&head, x);
            printList(head);
        }
        else if (l == 2) {
            int x;
            scanf("%d", &x);
            add_beg(&head, x);
            printList(head);
        }
        else if(l == 3) {
            int x, y;
            scanf("%d %d", &y, &x);
            if (getpos(head, y) == -1)
                add_end(&head, x);
            else {
                int t = getpos(head, y);
                addpos(head, x, t + 2);
            }
            printList(head);
        }
        else if (l == 4) {
            int x, y;
            scanf("%d %d", &y, &x);
            if (getpos(head, y) == -1)
                add_beg(&head, x);
            else {
                int t = getpos(head, y);
                if (t + 1 == 1)
                    add_beg(&head, x);
                else
                    addpos(head, x, t + 1);
            }
            printList(head);
        }
        else if (l == 5) {
            int x;
            scanf("%d", &x);
            int t = getpos(head, x);
            delpos(&head, t + 1);
            printList(head);
        }
        else if (l == 6) {
            int x;
            scanf("%d", &x);
            int t = getpos(head, x);
            if (t == -1) {
                printf("%d\n", t);
            } else {
                printf("%d\n", t+1);
            }
        }
        else if (l == 7) {
            head = reverse(head);
            printList(head);
        }
    }
}
    return 0;
}