使用链表和将元素传递到节点时遇到麻烦

Question

In this specific instance, it takes into account two occasions. One where I'm trying to place a node in the beginning of the Linked List and one where I'm trying to place it in the middle or at the end. Here is my Node Class. If you look at my INSERT method, the part that is not working is:

Node newNode = new Node();

newNode.setExponent(element);

class Node {

private int coefficient;
private int exponent;
private Node link;

// Constructor: Node()
Node(int c, int e) {
    // Sets coefficient to c, exponent to e, and link to null
    coefficient = c;
    exponent = e;
    link = null;
}

// Inspectors: getCoefficient(), getExponent(), getLink()
public int getCoefficient() {
    // Returns coefficient

    return coefficient;
}

public int getExponent() {
    // Returns exponent
    return exponent;
}

public Node getLink() {
    // Returns link
    return link;
}

// Modifiers: setCoefficient(), setExponent(), setLink()
public void setCoefficient(int c) {
    // Sets coefficient to c
    coefficient = c;
}

public void setExponent(int e) {
    // Sets exponent to e
    exponent = e;
}

public void setLink(Node n) {
    // Sets link to n
    link = n;
}
}// Ends Node Class

Here is where I'm trying to insert to my Linked List along with some other methods in the class that should help give you an idea of how my code looks.

class List {
private Node head; // Points to first element of the list
private int count; // number of elements in the list

// Constructor:
List() {
    // Sets head to null and count to zero
    head = null;
    count = 0;
}

// Inspectors:
// Returns the number of elements in the list
public int size() {
    return count;
}

// Modifiers:
// Inserts element at index in the list. Returns true if successful
public boolean insert(int index, Node element) {
    if (index < 0 || index > count)return false;
    if (index == 0) {
        Node newNode = new Node();
        newNode.setExponent(element);
        count++;
        newNode.setLink(head);
        head = newNode;
        return true;
    }
    Node walker = head;
    for (int i = 1; i < (index - 1); i++)
        walker = walker.getLink();
    Node newNode = new Node();
    newNode.setExponent(element);
    newNode.setLink(walker.getLink());
    walker.setLink(newNode);
    count++;
    return true;
}

Answer 1

Try this:

Assumption: You are trying to insert a Node element into the index of LinkedList

Your insert method with modification.

public boolean insert(int index, Node element) {
//if (index < 0 || index > count)
if (index < 0 || index > count + 1) return false;
if(head == null) {
    head = element;
    return true;
}
if (index == 0) {
    //Node newNode = new Node();
    //newNode.setExponent(element);
    count++;
    element.setLink(head);
    //newNode.setLink(head);
    head = element;
    //head = newNode;
    return true;
}
    Node walker = head;
    //for (int i = 0; i < (index - 1); i++)
    for (int i = 1; i < index; i++) {
        walker = walker.getLink();
    }
    //Node newNode = new Node();
    //newNode.setExponent(element);
    element.setLink(walker.getLink());
    //newNode.setLink(walker.getLink());
    //walker.setLink(newNode);
    walker.setLink(element);
    count++;
    return true;
}

Sample Test Case:

print method:

void print() {
    Node travel = head;
    while(travel!= null) {
        System.out.println(travel.getExponent() + " " + travel.getCoefficient());
        travel = travel.getLink();
    }
}

Main method:

public static void main(String args[]) {
    Node n1 = new Node(1,2);
    List l = new List();
    l.insert(0,n1);

    Node n2 = new Node(3,2);
    l.insert(1,n2);

    Node n3 = new Node(4,5);
    l.insert(0,n3);

    l.print();
}