C Exercises: Remove N^th node from the end of a singly linked list

Last update on December 20 2024 13:06:16 (UTC/GMT +8 hours)

Write a C program to remove the N^th node from the end of a singly linked list.

Sample Solution:

C Code:

#include<stdio.h>
#include <stdlib.h>

// Structure for defining a Node in a Singly Linked List
struct Node {
    int data; // Data stored in the node
    struct Node* next; // Pointer to the next node
};

// Function to create a new node in the Singly Linked List
struct Node* newNode(int data) {
    struct Node* node = (struct Node*) malloc(sizeof(struct Node)); // Allocate memory for a new node
    node->data = data; // Assign the data to the new node
    node->next = NULL; // Initialize next pointer as NULL
    return node; // Return the new node
}

// Function to remove the nth node from the end of a Singly Linked List
void remove_Nth_From_End(struct Node* head, int n) {
    struct Node *temp = head; // Initialize a temporary pointer to the head of the list
    int len = 0; // Variable to store the length of the list

    // Calculate the length of the linked list
    while (temp != NULL) {
        temp = temp->next;
        len++;
    }

    // Check if the given position to remove is valid
    if (len < n) {
        return; // If position is invalid (beyond list length), exit the function
    }

    temp = head; // Reset the temporary pointer to the head of the list

    // Traverse to the node just before the node to be removed
    for (int i = 1; i < len - n; i++) {
        temp = temp->next;
    }

    // Check if the node to be removed is the first node
    if (temp->next == NULL) {
        head = head->next; // Update head to the next node
        return;
    }

    struct Node *temp2 = temp->next; // Store the node to be removed in temp2
    temp->next = temp2->next; // Adjust pointers to remove the node
    free(temp2); // Free memory occupied by the removed node
}

// Function to print a linked list
void displayList(struct Node* head) {
    while (head) {
        printf("%d ", head->data); // Print the data of the current node
        head = head->next; // Move to the next node
    }
    printf("\n");
}

// Main function
int main() {
    struct Node* head = newNode(1); // Create a Singly Linked List with nodes containing data
    head->next = newNode(2);
    head->next->next = newNode(3);
    head->next->next->next = newNode(4);
    head->next->next->next->next = newNode(5);
    printf("Original Singly List:\n");
    displayList(head); // Print the original list

    printf("\nRemove 1st node from the end of a singly linked list:\n");
    remove_Nth_From_End(head, 1); // Remove the 1st node from the end
    displayList(head); // Print the updated list

    printf("\nRemove 3rd node from the end of a singly linked list:\n");
    remove_Nth_From_End(head, 3); // Remove the 3rd node from the end
    displayList(head); // Print the updated list

    return 0;
}

Sample Output:

Original Singly List:
1 2 3 4 5 

Remove 1st node from the end of a singly linked list:
1 2 3 4 

Remove 3rd node from the end of a singly linked list:
1 3 4 

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