Deletion of first node in singly link list

Now we will see how to delete node at first position in singly link list.

Algorithm to delete node at first position in singly link list:

Set TEMP = START
If START != NULL
- Make START points to second node i.e. [START = START->NEXT]
- FREE (TEMP)
End If

Function to delete node at first position in singly link list:


int deleteFirst(NODE **start){
 NODE *temp = *start;
 int info = -1;
 if(*start == NULL){
  printf("\nNo nodes exists in the list\n");
 }
 else{
  info = (*start)->info;
  *start = (*start)->next;
  free(temp);
 }
 return info;
}

Program to delete node at first position in the singly link list:


#include <stdio.h>
#include <malloc.h>

struct node{
 int info;
 struct node *next;
};
typedef struct node NODE;


void insertAtFirst(NODE **, int);
int deleteFirst(NODE **);
void traverse(NODE **);

int main(){
 
 NODE *start = NULL;
 
 insertAtFirst(&start, 4);
 insertAtFirst(&start, 5); 
 traverse(&start);
 deleteFirst(&start);
 printf("\n");
 traverse(&start);

 return 0;
}


int deleteFirst(NODE **start){
 NODE *temp = *start;
 int info = -1;
 if(*start == NULL){
  printf("\nNo nodes exists in the list\n");
 }
 else{
  info = (*start)->info;
  *start = (*start)->next;
  free(temp);
 }
 return info;
}

void insertAtFirst(NODE **start, int info){
 NODE *ptr = (NODE*) malloc(sizeof(NODE));
 ptr->info = info;
 ptr->next = *start;
 *start = ptr; 
}

void traverse(NODE **start){
 NODE *temp;
 temp = *start;
 while(temp != NULL){
  printf("%d  ", temp->info);
  temp = temp->next;
 }
}

Output:

5  4
4

Comments

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