How to remove last element from a chained list using position?

Question

I am wanting to remove the last element from a chained list by typing position n:

when I type 1,2,3,4,5 of and n=2, I want it to stay 1,2,3,5 but it’s giving 1,2,3.

import java.io.IOException;
import java.util.Scanner;

class No {
    int val;
    No prox;

    No(int x) {
        val = x;
    }
}

public class Main {
    public static No removeNElementoDoFim(No cabeca, int n) {

        if (cabeca == null) {
            return null;
        } else {
            No ultimoNo = cabeca.prox;
            No penultimoNo = cabeca.prox;
            for (int i = 0; ultimoNo.prox != null && i < n; i++) {
                penultimoNo = ultimoNo;
                ultimoNo = ultimoNo.prox;
            }
            penultimoNo.prox = null;
            return cabeca;
        }

    }

    public static int[] stringToIntegerArray(String input) {
        input = input.trim();
        if (input.length() == 0) {
            return new int[0];
        }

        String[] parts = input.split(",");
        int[] output = new int[parts.length];
        for (int index = 0; index < parts.length; index++) {
            if (parts[index].trim().length() > 0) {
                String part = parts[index].trim();
                output[index] = Integer.parseInt(part);
            }
        }
        return output;
    }

    public static No stringToNo(String input) {

        int[] nodeValues = stringToIntegerArray(input);

        No root = new No(0);
        No ptr = root;
        for (int item : nodeValues) {
            ptr.prox = new No(item);
            ptr = ptr.prox;
        }
        return root.prox;
    }

    public static String noToString(No no) {
        if (no == null) {
            return "[]";
        }

        String result = "";
        while (no != null) {
            result += Integer.toString(no.val) + ", ";
            no = no.prox;
        }
        return "[" + result.substring(0, result.length() - 2) + "]";
    }

    public static void main(String[] args) throws IOException {
        Scanner scann = new Scanner(System.in);
        String line;
        while (scann.hasNextLine()) {
            line = scann.nextLine();
            No cabeca = stringToNo(line);

            int n = Integer.valueOf(scann.nextLine());

            No ret = removeNElementoDoFim(cabeca, n);

            String out = noToString(ret);

            System.out.print(out);
        }

        scann.close();
    }
}

Answer 1

Well, come on. I’m assuming it’s a simple chained list. I’ll tell you the logic:

Within the method that will receive an n value, you will: 1. Check that the list is not empty 2. If you have made an attribute for the list size, check that the entered value is less than or equal to the size (whereas the user type 0 for the first value). 3. If yes, you are a minor, you will do the following: 4. Create a new helper pointer getting the start (we do this so we don’t have to change the start pointer), example:

no *aux = inicio;

int i;
for(i=0;i<posicao-1;i++) {
   aux = aux.prox;
}

Now, we need to update the pointers:

aux.next = aux.next.next;
tam--;

As in java has "garbage collector", we do not need to delete aux we created.

You can include this in the beginning:

   if(posicao<tam && posicao>=0){
     if(posicao==0){
         removerinicio();
   }

If the user type 0! Hugs!!!

Answer 2

I managed to solve it, but not in the right way:

import java.io.IOException;
import java.util.Scanner;

class No {
    int val;
    No prox;

    No(int x) {
        val = x;
    }
}

public class Main {

    public static No removeNElementoDoFim(No cabeca, int n) {

        // Coloque seu código aqui
        No aux = cabeca;
        if (cabeca == null) {
            return null;
        } else {
            for (int i = 0; i < n - 1; i++) {
                aux.prox.prox.prox = aux.prox.prox.prox.prox;
            }

            return aux;
        }
    }

    public static int[] stringToIntegerArray(String input) {
        input = input.trim();
        if (input.length() == 0) {
            return new int[0];
        }

        String[] parts = input.split(",");
        int[] output = new int[parts.length];
        for (int index = 0; index < parts.length; index++) {
            if (parts[index].trim().length() > 0) {
                String part = parts[index].trim();
                output[index] = Integer.parseInt(part);
            }
        }
        return output;
    }

    public static No stringToNo(String input) {

        int[] nodeValues = stringToIntegerArray(input);

        No root = new No(0);
        No ptr = root;
        for (int item : nodeValues) {
            ptr.prox = new No(item);
            ptr = ptr.prox;
        }
        return root.prox;
    }

    public static String noToString(No no) {
        if (no == null) {
            return "[]";
        }

        String result = "";
        while (no != null) {
            result += Integer.toString(no.val) + ", ";
            no = no.prox;
        }
        return "[" + result.substring(0, result.length() - 2) + "]";
    }

    public static void main(String[] args) throws IOException {
        Scanner scann = new Scanner(System.in);
        String line;
        while (scann.hasNextLine()) {
            line = scann.nextLine();
            No cabeca = stringToNo(line);

            int n = Integer.valueOf(scann.nextLine());

            No ret = removeNElementoDoFim(cabeca, n);

            String out = noToString(ret);

            System.out.print(out);
        }

        scann.close();
    }
}