D will be the answer.
if we implement the given function:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 10
struct node {
int data;
struct node *next;
};
// function f() for this question
void f(struct node *P) {
if(P != NULL)
f(P->next);
// if(P != NULL) // without this line segmentation fault
printf(" %d\n",P->data);
}
// helper function
void print_elem(struct node *P) {
while(P != NULL) {
printf(" %d -> ",P->data);
P = P->next;
}
if(!P) printf("NULL\n");
}
void deallocate_list_memory(struct node* P);
int main() {
srand(time(NULL));
int i=0;
struct node *head;
head = NULL;
// inserting 10 random data items between 0 to 9 including
struct node *temp = NULL; // helper node pointer
for(i=0;i<N;i++) {
struct node *new_node = (struct node*)malloc(sizeof(struct node));
// first create a node with data
int val = rand()%10;
new_node->data = val;
new_node->next = NULL;
// now link the newly created node with
// exisiting chain (list)
// if list is empty
if(temp == NULL) {
head = new_node; // set the parent node pointer first
temp = new_node; // set the helper node pointer
printf(" %d is inserted \n",val);
}
// if list not empty
else {
temp->next = new_node;
temp = new_node;
printf(" %d is inserted \n",val);
}
}
printf("\n printing the inserted elements\n\n");
print_elem(head);
// For this question call f()
printf("\n\n output of given function in the question\n");
f(head);
deallocate_list_memory(head);
return 0;
}
// imp to deallocate
void deallocate_list_memory(struct node* P) {
struct node *temp;
while(P != NULL) {
temp = P;
P = P->next;
free(temp);
}
}
O/P : segmentation fault.
Reason :
while f() is calling recursively itself, there will be a situation like this in the above image at some point of time.
The next call to f() will be f(P->next).
But there is no code before printf to handle the null, which will result in segmentation fault.
one possible fix in the above code to print in the elements in reverse order is to add if(P != NULL) before printing the data inside P.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 10
struct node {
int data;
struct node *next;
};
// function f() for this question
void f(struct node *P) {
if(P != NULL)
f(P->next);
if(P != NULL) // without this line segmentation fault
printf(" %d\n",P->data);
}
// helper function
void print_elem(struct node *P) {
while(P != NULL) {
printf(" %d -> ",P->data);
P = P->next;
}
if(!P) printf("NULL\n");
}
void deallocate_list_memory(struct node* P);
int main() {
srand(time(NULL));
int i=0;
struct node *head;
head = NULL;
// inserting 10 random data items between 0 to 9 including
struct node *temp = NULL; // helper node pointer
for(i=0;i<N;i++) {
struct node *new_node = (struct node*)malloc(sizeof(struct node));
// first create a node with data
int val = rand()%10;
new_node->data = val;
new_node->next = NULL;
// now link the newly created node with
// exisiting chain (list)
// if list is empty
if(temp == NULL) {
head = new_node; // set the parent node pointer first
temp = new_node; // set the helper node pointer
printf(" %d is inserted \n",val);
}
// if list not empty
else {
temp->next = new_node;
temp = new_node;
printf(" %d is inserted \n",val);
}
}
printf("\n printing the inserted elements\n\n");
print_elem(head);
// For this question call f()
printf("\n\n output of given function in the question\n");
f(head);
deallocate_list_memory(head);
return 0;
}
// imp to deallocate
void deallocate_list_memory(struct node* P) {
struct node *temp;
while(P != NULL) {
temp = P;
P = P->next;
free(temp);
}
}
O/P :
2 is inserted
3 is inserted
2 is inserted
2 is inserted
1 is inserted
6 is inserted
1 is inserted
2 is inserted
9 is inserted
4 is inserted
printing the inserted elements
2 -> 3 -> 2 -> 2 -> 1 -> 6 -> 1 -> 2 -> 9 -> 4 -> NULL
output of given function in the question
4
9
2
1
6
1
2
2
3
2
