Given a singly linked list and a position, delete a linked list node at the given position.
Example:
Input: position = 1, Linked List = 8->2->3->1->7 Output: Linked List = 8->3->1->7 Input: position = 0, Linked List = 8->2->3->1->7 Output: Linked List = 2->3->1->7
If node to be deleted is root, simply delete it. To delete a middle node, we must have pointer to the node previous to the node to be deleted. So if positions is not zero, we run a loop position-1 times and get pointer to the previous node.
Below is the implementation of above idea.
C/C++
// A complete working C program to delete a node in a linked list // at a given position #include <stdio.h> #include <stdlib.h> // A linked list node struct Node { int data; struct Node *next; }; /* Given a reference (pointer to pointer) to the head of a list and an int, inserts a new node on the front of the list. */void push(struct Node** head_ref, int new_data) { struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); new_node->data = new_data; new_node->next = (*head_ref); (*head_ref) = new_node; } /* Given a reference (pointer to pointer) to the head of a list and a position, deletes the node at the given position */void deleteNode(struct Node **head_ref, int position) { // If linked list is empty if (*head_ref == NULL) return; // Store head node struct Node* temp = *head_ref; // If head needs to be removed if (position == 0) { *head_ref = temp->next; // Change head free(temp); // free old head return; } // Find previous node of the node to be deleted for (int i=0; temp!=NULL && i<position-1; i++) temp = temp->next; // If position is more than number of ndoes if (temp == NULL || temp->next == NULL) return; // Node temp->next is the node to be deleted // Store pointer to the next of node to be deleted struct Node *next = temp->next->next; // Unlink the node from linked list free(temp->next); // Free memory temp->next = next; // Unlink the deleted node from list } // This function prints contents of linked list starting from // the given node void printList(struct Node *node) { while (node != NULL) { printf(" %d ", node->data); node = node->next; } } /* Drier program to test above functions*/int main() { /* Start with the empty list */ struct Node* head = NULL; push(&head, 7); push(&head, 1); push(&head, 3); push(&head, 2); push(&head, 8); puts("Created Linked List: "); printList(head); deleteNode(&head, 4); puts("
Linked List after Deletion at position 4: "); printList(head); return 0; } |
Java
// A complete working Java program to delete a node in a linked list // at a given position class LinkedList { Node head; // head of list /* Linked list Node*/ class Node { int data; Node next; Node(int d) { data = d; next = null; } } /* Inserts a new Node at front of the list. */ public void push(int new_data) { /* 1 & 2: Allocate the Node & Put in the data*/ Node new_node = new Node(new_data); /* 3. Make next of new Node as head */ new_node.next = head; /* 4. Move the head to point to new Node */ head = new_node; } /* Given a reference (pointer to pointer) to the head of a list and a position, deletes the node at the given position */ void deleteNode(int position) { // If linked list is empty if (head == null) return; // Store head node Node temp = head; // If head needs to be removed if (position == 0) { head = temp.next; // Change head return; } // Find previous node of the node to be deleted for (int i=0; temp!=null && i<position-1; i++) temp = temp.next; // If position is more than number of ndoes if (temp == null || temp.next == null) return; // Node temp->next is the node to be deleted // Store pointer to the next of node to be deleted Node next = temp.next.next; temp.next = next; // Unlink the deleted node from list } /* This function prints contents of linked list starting from the given node */ public void printList() { Node tnode = head; while (tnode != null) { System.out.print(tnode.data+" "); tnode = tnode.next; } } /* Drier program to test above functions. Ideally this function should be in a separate user class. It is kept here to keep code compact */ public static void main(String[] args) { /* Start with the empty list */ LinkedList llist = new LinkedList(); llist.push(7); llist.push(1); llist.push(3); llist.push(2); llist.push(8); System.out.println("
Created Linked list is: "); llist.printList(); llist.deleteNode(4); // Delete node at position 4 System.out.println("
Linked List after Deletion at position 4: "); llist.printList(); } } |
Python
# Python program to delete a node in a linked list # at a given position # Node class class Node: # Constructor to initialize the node object def __init__(self, data): self.data = data self.next = None class LinkedList: # Constructor to initialize head def __init__(self): self.head = None # Function to insert a new node at the beginning def push(self, new_data): new_node = Node(new_data) new_node.next = self.head self.head = new_node # Given a reference to the head of a list # and a position, delete the node at a given position def deleteNode(self, position): # If linked list is empty if self.head == None: return # Store head node temp = self.head # If head needs to be removed if position == 0: self.head = temp.next temp = None return # Find previous node of the node to be deleted for i in range(position -1 ): temp = temp.next if temp is None: break # If position is more than number of nodes if temp is None: return if temp.next is None: return # Node temp.next is the node to be deleted # store pointer to the next of node to be deleted next = temp.next.next # Unlink the node from linked list temp.next = None temp.next = next # Utility function to print the linked LinkedList def printList(self): temp = self.head while(temp): print " %d " %(temp.data), temp = temp.next # Driver program to test above function llist = LinkedList() llist.push(7) llist.push(1) llist.push(3) llist.push(2) llist.push(8) print "Created Linked List: "llist.printList() llist.deleteNode(4) print "
Linked List after Deletion at position 4: "llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007) |
Output:
Created Linked List: 8 2 3 1 7 Linked List after Deletion at position 4: 8 2 3 1
Thanks to Hemanth Kumar for suggesting initial solution. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
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