Description

To delete a node before given node singly linked list - 
Case 1: check if list is empty 
	Show message that list is empty.
Case 2: If list has only one element
	Show message that no node available before that node to delete.
Case 3: If to delete a node before second node
	Step 1: Delete first node
	Step 2: Make second node as first node
	Step 3: Free the memory occupied by first node
Case 4: If to delete any other node..
	Step 1: Traverse the list to reach that node before which a node to delete
	Step 2: Maintain the two node which contain the address of previous node
	(preAddress) and previous to previous node(tempAddress). 
	Step 3: Assign the address of node before which node to delete to the address
	field of previous to previous node.
	Step 4: Free the memory occupied by node.

Note: Here head contains the address of first node

C/C++

/* C Program To Delete a Node before given node In singly linked list */
//Save it as delete_node_before_given_node_singly_linked_list.c

#include<stdio.h>
#include<malloc.h>
struct node *create(int);
void display(struct node *);
struct node *delete_node_before_given_node(struct node *);

//Declaring node
struct node{
    int data;
    struct node *next;
};

int main(){
    int n;
    struct node *head;
    printf("Enter number of nodes : ");
    scanf("%d",&n);
    
    //Calling function to create node
    head=create(n);
    
    //Calling function to display list
    display(head);
    
    //Code to delete a node before a given node
    head=delete_node_before_given_node(head);
    printf("\nThe linked list after deletion of a node before given node - \n");
    
    //Calling function to display list after deletion of a node before given node
    display(head);

    return 0;
}

struct node *create(int n){
    int i;
    struct node *head=NULL;
    struct node *ptr,*newNode;

    for(i=0;i<n;i++){
        
        //Creating a new node
        newNode=(struct node*)malloc(sizeof(struct node*));
        
        //Assigning data to newly created node
        printf("Enter the value of %d node : ",i+1);
        scanf("%d",&newNode->data);
        newNode->next=NULL;
        
        /*If list is empty assign the address of newly created node to head*/
        if(head==NULL){
            head=newNode;
        }else{
            
            /* If list already have few elements then loop through
            list and add newly created node after given node*/
            ptr=head;
            while(ptr->next!=NULL){
                ptr=ptr->next;
            }
            ptr->next=newNode;
        }
    }
    return head;
}

void display(struct node *head){
    struct node *ptr;
    
    //If list is empty
    if(head==NULL){
        printf("The linked list is empty");
    }else{
        
        /*If list has elements then loop through the loop and
        print elements one by one in sequential manner*/
        ptr=head;
        while(ptr!=NULL){
            printf("The node value = %d and their address = %u\n",ptr->data,ptr);
            ptr=ptr->next;
        }
    }
}

//Function to delete a node before a given node
struct node *delete_node_before_given_node(struct node *head){
    int val;
    struct node *address, *preAddress, *tempAddress;

    printf("\nEnter the value before which node to delete : ");
    scanf("%d",&val);
    
    //If list is empty, show message
    if(head==NULL){
        printf("\nNo node available to delete!!");
    }
    
    //If list has only one node
    else if(head->next==NULL){
        printf("No any previous node available to delete!!");
    }
    
    //If list has more than one elements
    else{
        address=head;
        tempAddress=head;
        preAddress=head;
        
        //Traverse the list to reach the given node
        while(address->data!=val){
            tempAddress=preAddress;
            preAddress=address;
            address=address->next;
        }
        
        //If need to delete node before second node means to delete first node
        if(address==head->next){
            head=address;
            free(preAddress);
        }
        
        //If trying to delete first node.
        else if(address==head){
            printf("No any previous node available to delete!!");
        }
        
        //For rest of the condition
        else{
            tempAddress->next=address;
            free(preAddress);
        }
    }
    return head;
}

Input:
Enter number of nodes : 4
Enter the value of 1 node : 2
Enter the value of 2 node : 5
Enter the value of 3 node : 3
Enter the value of 4 node : 7
The node value = 2 and their address = 9899360
The node value = 5 and their address = 9899392
The node value = 3 and their address = 9899408
The node value = 7 and their address = 9899424

Enter the value before which node to delete : 7

Output:
The linked list after deletion of a node before given node -
The node value = 2 and their address = 9899360
The node value = 5 and their address = 9899392
The node value = 7 and their address = 9899424

Java

/* Java Program To Delete a Node before given node In singly linked list */
//Save it as DeleteNodeBeforeGivenNodeSinglyLinkedList.java

import java.io.*;
import java.util.Scanner;

public class DeleteNodeBeforeGivenNodeSinglyLinkedList {
    
    // Declaring node
    class Node {
        int data;
        Node next;

        public Node(int data) {
            this.data = data;
            
            // Assigning null value to the next field
            this.next = null;
        }
    }

    public Node head = null;
    
    // Function to add node
    public void addNode(int data) {
        
        // Creating a new node
        Node newNode = new Node(data);
        
        /* If list is empty assign the address of newly created node to head */
        if (head == null) {
            head = newNode;
        } else {
            
            /*
             * If list already have few elements then loop through list and
             */
            Node ptr = head;
            while (ptr.next != null) {
                ptr = ptr.next;
            }
            ptr.next = newNode;
        }
    }

    public void display() {
        Node ptr = head;
        
        // If list is empty
        if (ptr == null) {
            System.out.println("The list is empty");
            return;
        }
        System.out.println("The nodes of lists are : ");
        
        /*
         * If list has elements then loop through the loop and print elements one by one
         * in sequential manner
         */
        while (ptr != null) {
            System.out.print(ptr.data + " ");
            ptr = ptr.next;
        }
    }

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        DeleteNodeBeforeGivenNodeSinglyLinkedList list = new DeleteNodeBeforeGivenNodeSinglyLinkedList();

        System.out.println("Enter number of node you want to enter : ");
        int n = scanner.nextInt();

        for (int i = 0; i < n; i++) {
            System.out.println("Enter value of " + (i + 1) + " node : ");
            int val = scanner.nextInt();
            list.addNode(val);
        }
        
        // Calling function to display list
        list.display();

        System.out.println("\nEnter the value before which node to delete : ");
        int val = scanner.nextInt();

        list.delete_node_before_given_node(val);
        
        // Calling function to display list after deletion of a node before given node
        System.out.println("\nAfter deletion of a node before given node - ");
        list.display();
    }

    private void delete_node_before_given_node(int val) {
        
        Node address, preAddress, tempAddress;
        
        //If list is empty, show message
        if(head==null) {
            System.out.println("No node available to delete!!");
        }
        
        //If list has only one node
        else if(head.next==null){
            System.out.println("No any previous node available to delete!!");
        }
        
        //If list has more than one elements
        else{
            address=head;
            tempAddress=head;
            preAddress=head;
            
            //Traverse the list to reach the given node
            while(address.data!=val){
                tempAddress=preAddress;
                preAddress=address;
                address=address.next;
            }
            
            //If need to delete node before second node means to delete first node
            if(address==head.next){
                head=address;
            }
            
            //If trying to delete first node.
            else if(address==head){
                System.out.println("No any previous node available to delete!!");
            }
            
            //For rest of the condition
            else{
                tempAddress.next=address;
            }
        }
    }
}

Input:
Enter number of node you want to enter : 
4
Enter value of 1 node : 
2
Enter value of 2 node : 
5
Enter value of 3 node : 
3
Enter value of 4 node : 
7
The nodes of lists are : 
2 5 3 7 
Enter the value before which node to delete : 
5

Output:
After deletion of a node before given node - 
The nodes of lists are : 
5 3 7

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