Delete last occurrence of an item from linked list

Loop through the whole list and use a double pointer to keep track of the node containing the address of last occurrence node.

#include <stdio.h> 
#include <stdlib.h> 
  
// A linked list Node 
struct Node { 
    int data; 
    struct Node* next; 
}; 
  
// Function to delete the last occurrence 
void deleteLast(struct Node** head, int x) 
{ 
        struct Node** tmp1 = NULL; 
        while(*head) { 
                if((*head)->data == x) { 
                        tmp1 = head; 
                } 
                head = &(*head)->next; 
        } 
        if(tmp1) { 
                struct Node* tmp = *tmp1; 
                *tmp1 = tmp->next; 
                free(tmp); 
        } 
} 
  
/* Utility function to create a new node with 
given key */
struct Node* newNode(int x) 
{ 
    struct Node* node = malloc(sizeof(struct Node*)); 
    node->data = x; 
    node->next = NULL; 
    return node; 
} 
  
// This function prints contents of linked list 
// starting from the given Node 
void display(struct Node* head) 
{ 
    struct Node* temp = head; 
    if (head == NULL) { 
        printf("NULL\n"); 
        return; 
    } 
    while (temp != NULL) { 
        printf("%d --> ", temp->data); 
        temp = temp->next; 
    } 
    printf("NULL\n"); 
} 
  
/* Drier program to test above functions*/
int main() 
{ 
    struct Node* head = newNode(1); 
    head->next = newNode(2); 
    head->next->next = newNode(3); 
    head->next->next->next = newNode(4); 
    head->next->next->next->next = newNode(5); 
    head->next->next->next->next->next = newNode(4); 
    head->next->next->next->next->next->next = newNode(4); 
    printf("Created Linked list: "); 
    display(head); 
    deleteLast(&head, 4);   // Pass the address of the head pointer 
    printf("List after deletion of 4: "); 
    display(head); 
    return 0; 
} 

Given a liked list and a key to be deleted. Delete last occurrence of key from linked. The list may have duplicates.

Examples:

Input:   1->2->3->5->2->10, key = 2
Output:  1->2->3->5->10

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

The idea is to traverse the linked list from beginning to end. While traversing, keep track of last occurrence key. After traversing the complete list, delete last occurrence by copying data of next node and deleting the next node.

C++

// A C++ program to demonstrate deletion of last 
// Node in singly linked list 
#include <bits/stdc++.h> 
  
// A linked list Node 
struct Node { 
    int key; 
    struct Node* next; 
}; 
  
void deleteLast(Node* head, int key) 
{ 
    // Initialize previous of Node to be deleted 
    Node* x = NULL; 
  
    // Start from head and find the Node to be 
    // deleted 
    Node* temp = head; 
    while (temp) { 
        // If we found the key, update xv 
        if (temp->key == key) 
            x = temp; 
  
        temp = temp->next; 
    } 
  
    // key occurs at-least once 
    if (x != NULL) { 
  
        // Copy key of next Node to x 
        x->key = x->next->key; 
  
        // Store and unlink next 
        temp = x->next; 
        x->next = x->next->next; 
  
        // Free memory for next 
        delete temp; 
    } 
} 
  
/* Utility function to create a new node with 
   given key */
Node* newNode(int key) 
{ 
    Node* temp = new Node; 
    temp->key = key; 
    temp->next = NULL; 
    return temp; 
} 
  
// This function prints contents of linked list 
// starting from the given Node 
void printList(struct Node* node) 
{ 
    while (node != NULL) { 
        printf(" %d ", node->key); 
        node = node->next; 
    } 
} 
  
/* Drier program to test above functions*/
int main() 
{ 
    /* Start with the empty list */
    struct Node* head = newNode(1); 
    head->next = newNode(2); 
    head->next->next = newNode(3); 
    head->next->next->next = newNode(5); 
    head->next->next->next->next = newNode(2); 
    head->next->next->next->next->next = newNode(10); 
  
    puts("Created Linked List: "); 
    printList(head); 
    deleteLast(head, 2); 
    puts("\nLinked List after Deletion of 1: "); 
    printList(head); 
    return 0; 
} 

Java

// A Java program to demonstrate deletion of last  
// Node in singly linked list  
class GFG 
{ 
      
  
// A linked list Node  
static class Node  
{  
    int key;  
    Node next;  
};  
  
static Node deleteLast(Node head, int key)  
{  
    // Initialize previous of Node to be deleted  
    Node x = null;  
  
    // Start from head and find the Node to be  
    // deleted  
    Node temp = head;  
    while (temp != null)  
    {  
        // If we found the key, update xv  
        if (temp.key == key)  
            x = temp;  
  
        temp = temp.next;  
    }  
  
    // key occurs at-least once  
    if (x != null)  
    {  
  
        // Copy key of next Node to x  
        x.key = x.next.key;  
  
        // Store and unlink next  
        temp = x.next;  
        x.next = x.next.next;  
  
        // Free memory for next  
    }  
    return head; 
}  
  
/// Utility function to create a new node with  
//given key / 
static Node newNode(int key)  
{  
    Node temp = new Node();  
    temp.key = key;  
    temp.next = null;  
    return temp;  
}  
  
// This function prints contents of linked list  
// starting from the given Node  
static void printList( Node node)  
{  
    while (node != null)  
    {  
        System.out.printf(" %d ", node.key);  
        node = node.next;  
    }  
}  
  
// Driver code/ 
public static void main(String args[]) 
{  
    // /Start with the empty list / 
    Node head = newNode(1);  
    head.next = newNode(2);  
    head.next.next = newNode(3);  
    head.next.next.next = newNode(5);  
    head.next.next.next.next = newNode(2);  
    head.next.next.next.next.next = newNode(10);  
  
    System.out.printf("Created Linked List: ");  
    printList(head);  
    deleteLast(head, 2);  
    System.out.printf("\nLinked List after Deletion of 1: ");  
    printList(head);  
} 
}  
  
// This code is contributed by Arnab Kundu 

C#

// C# program to demonstrate deletion of last  
// Node in singly linked list  
using System; 
  
class GFG  
{  
      
  
// A linked list Node  
public class Node  
{  
    public int key;  
    public Node next;  
};  
  
static Node deleteLast(Node head, int key)  
{  
    // Initialize previous of Node to be deleted  
    Node x = null;  
  
    // Start from head and find the Node to be  
    // deleted  
    Node temp = head;  
    while (temp != null)  
    {  
        // If we found the key, update xv  
        if (temp.key == key)  
            x = temp;  
  
        temp = temp.next;  
    }  
  
    // key occurs at-least once  
    if (x != null)  
    {  
  
        // Copy key of next Node to x  
        x.key = x.next.key;  
  
        // Store and unlink next  
        temp = x.next;  
        x.next = x.next.next;  
  
        // Free memory for next  
    }  
    return head;  
}  
  
/// Utility function to create a new node with  
//given key /  
static Node newNode(int key)  
{  
    Node temp = new Node();  
    temp.key = key;  
    temp.next = null;  
    return temp;  
}  
  
// This function prints contents of linked list  
// starting from the given Node  
static void printList( Node node)  
{  
    while (node != null)  
    {  
        Console.Write(" {0} ", node.key);  
        node = node.next;  
    }  
}  
  
// Driver code/  
public static void Main(String []args)  
{  
    // /Start with the empty list /  
    Node head = newNode(1);  
    head.next = newNode(2);  
    head.next.next = newNode(3);  
    head.next.next.next = newNode(5);  
    head.next.next.next.next = newNode(2);  
    head.next.next.next.next.next = newNode(10);  
  
    Console.Write("Created Linked List: ");  
    printList(head);  
    deleteLast(head, 2);  
    Console.Write("\nLinked List after Deletion of 1: ");  
    printList(head);  
}  
}  
  
// This code has been contributed by 29AjayKumar 

Output:

Created Linked List: 
 1  2  3  5  2  10 
Linked List after Deletion of 1: 
 1  2  3  5  10

The above solution doesn’t work when the node to be deleted is the last node.

Following solution handles all cases.

C++

// A C program to demonstrate deletion of last 
// Node in singly linked list 
#include <stdio.h> 
#include <stdlib.h> 
  
// A linked list Node 
struct Node { 
    int data; 
    struct Node* next; 
}; 
  
// Function to delete the last occurrence 
void deleteLast(struct Node* head, int x) 
{ 
    struct Node *temp = head, *ptr = NULL; 
    while (temp) { 
  
        // If found key, update 
        if (temp->data == x)  
            ptr = temp;         
        temp = temp->next; 
    } 
  
    // If the last occurrence is the last node 
    if (ptr != NULL && ptr->next == NULL) { 
        temp = head; 
        while (temp->next != ptr)  
            temp = temp->next;        
        temp->next = NULL; 
    } 
  
    // If it is not the last node 
    if (ptr != NULL && ptr->next != NULL) { 
        ptr->data = ptr->next->data; 
        temp = ptr->next; 
        ptr->next = ptr->next->next; 
        free(temp); 
    } 
} 
  
/* Utility function to create a new node with 
given key */
struct Node* newNode(int x) 
{ 
    struct Node* node = malloc(sizeof(struct Node*)); 
    node->data = x; 
    node->next = NULL; 
    return node; 
} 
  
// This function prints contents of linked list 
// starting from the given Node 
void display(struct Node* head) 
{ 
    struct Node* temp = head; 
    if (head == NULL) { 
        printf("NULL\n"); 
        return; 
    } 
    while (temp != NULL) { 
        printf("%d --> ", temp->data); 
        temp = temp->next; 
    } 
    printf("NULL\n"); 
} 
  
/* Drier program to test above functions*/
int main() 
{ 
    struct Node* head = newNode(1); 
    head->next = newNode(2); 
    head->next->next = newNode(3); 
    head->next->next->next = newNode(4); 
    head->next->next->next->next = newNode(5); 
    head->next->next->next->next->next = newNode(4); 
    head->next->next->next->next->next->next = newNode(4); 
    printf("Created Linked list: "); 
    display(head); 
    deleteLast(head, 4); 
    printf("List after deletion of 4: "); 
    display(head); 
    return 0; 
}

Java

// Java program to demonstrate deletion of last  
// Node in singly linked list  
class GFG  
{ 
  
// A linked list Node  
static class Node  
{  
    int data;  
    Node next;  
};  
  
// Function to delete the last occurrence  
static void deleteLast(Node head, int x)  
{  
    Node temp = head, ptr = null;  
    while (temp!=null)  
    {  
  
        // If found key, update  
        if (temp.data == x)  
            ptr = temp;      
        temp = temp.next;  
    }  
  
    // If the last occurrence is the last node  
    if (ptr != null && ptr.next == null)  
    {  
        temp = head;  
        while (temp.next != ptr)  
            temp = temp.next;  
        temp.next = null;  
    }  
  
    // If it is not the last node  
    if (ptr != null && ptr.next != null) 
    {  
        ptr.data = ptr.next.data;  
        temp = ptr.next;  
        ptr.next = ptr.next.next;  
        System.gc(); 
    }  
}  
  
/* Utility function to create a new node with  
given key */
static Node newNode(int x)  
{  
    Node node = new Node();  
    node.data = x;  
    node.next = null;  
    return node;  
}  
  
// This function prints contents of linked list  
// starting from the given Node  
static void display(Node head)  
{  
    Node temp = head;  
    if (head == null)  
    {  
        System.out.print("null\n");  
        return;  
    }  
    while (temp != null)  
    {  
        System.out.printf("%d --> ", temp.data);  
        temp = temp.next;  
    }  
    System.out.print("null\n");  
}  
  
/* Driver code*/
public static void main(String[] args)  
{ 
    Node head = newNode(1);  
    head.next = newNode(2);  
    head.next.next = newNode(3);  
    head.next.next.next = newNode(4);  
    head.next.next.next.next = newNode(5);  
    head.next.next.next.next.next = newNode(4);  
    head.next.next.next.next.next.next = newNode(4);  
    System.out.print("Created Linked list: ");  
    display(head);  
    deleteLast(head, 4);  
    System.out.print("List after deletion of 4: ");  
    display(head);  
} 
} 
  
/* This code is contributed by PrinciRaj1992 */

C#

// C# program to demonstrate deletion of last  
// Node in singly linked list  
using System; 
  
class GFG  
{ 
  
// A linked list Node  
public class Node  
{  
    public int data;  
    public Node next;  
};  
  
// Function to delete the last occurrence  
static void deleteLast(Node head, int x)  
{  
    Node temp = head, ptr = null;  
    while (temp != null)  
    {  
  
        // If found key, update  
        if (temp.data == x)  
            ptr = temp;      
        temp = temp.next;  
    }  
  
    // If the last occurrence is the last node  
    if (ptr != null && ptr.next == null)  
    {  
        temp = head;  
        while (temp.next != ptr)  
            temp = temp.next;  
        temp.next = null;  
    }  
  
    // If it is not the last node  
    if (ptr != null && ptr.next != null) 
    {  
        ptr.data = ptr.next.data;  
        temp = ptr.next;  
        ptr.next = ptr.next.next;  
    }  
}  
  
/* Utility function to create a new node with  
given key */
static Node newNode(int x)  
{  
    Node node = new Node();  
    node.data = x;  
    node.next = null;  
    return node;  
}  
  
// This function prints contents of linked list  
// starting from the given Node  
static void display(Node head)  
{  
    Node temp = head;  
    if (head == null)  
    {  
        Console.Write("null\n");  
        return;  
    }  
    while (temp != null)  
    {  
        Console.Write("{0} --> ", temp.data);  
        temp = temp.next;  
    }  
    Console.Write("null\n");  
}  
  
/* Driver code*/
public static void Main(String[] args)  
{ 
    Node head = newNode(1);  
    head.next = newNode(2);  
    head.next.next = newNode(3);  
    head.next.next.next = newNode(4);  
    head.next.next.next.next = newNode(5);  
    head.next.next.next.next.next = newNode(4);  
    head.next.next.next.next.next.next = newNode(4);  
    Console.Write("Created Linked list: ");  
    display(head);  
    deleteLast(head, 4);  
    Console.Write("List after deletion of 4: ");  
    display(head);  
} 
} 
  
// This code contributed by Rajput-Ji 

Output:

Created Linked List: 
 1  2  3  4  5  4  4 
Linked List after Deletion of 1: 
 1  2  3  4  5  4

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Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

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C++

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