// Polynomial.java
public class Polynomial
{
private int degree;
private Node head;

public static Polynomial addPolys(Polynomial poly1, Polynomial poly2)
{
Polynomial polyRes = new Polynomial();
int power = (poly1.degree > poly2.degree) ? poly1.degree : poly2.degree;

while (power >= 0)
{
Node n1 = poly1.head;
while (n1 != null)
{
if (n1.power == power)
break;
n1 = n1.next;
}

Node n2 = poly2.head;
while (n2 != null)
{
if (n2.power == power)
break;
n2 = n2.next;
}

if ((n1 != null) && (n2 != null))
polyRes.addNode(n1.coeff + n2.coeff, n1.power);
else if (n1 != null)
polyRes.addNode(n1.coeff, n1.power);
else if (n2 != null)
polyRes.addNode(n2.coeff, n2.power);

power--;
}
return polyRes;
}

public void addNode(int coeff, int power)
{
if (head == null) // start the list
{
head = new Node(coeff, power, null);
degree = power;
}
else
{
Node n = head;
Node last = null;

while (n != null)
{
if (power > n.power) // insert in list
{
if (last == null)
head = new Node(coeff, power, n);
else
last.next = new Node(coeff, power, n);
degree = power;
break;
}
last = n;
n = n.next;
}
if (n == null) // append to list
{
last.next = new Node(coeff, power, null);
}
}
}

//loop though the nodes until we got to the desired index - 1 and keep the reference of the node as A (A is the node right before the node we want to remove)
public void removeNode(int indexnumber)
{
Node n = head;
int i = 0;
while (i < indexnumber - 1){
n = n.next;
if(n.next == null)
//throw exception
++i;
}
Node A = n;
//(if we encounter a node with the next node pointing to null, thow an exception)
Node B = A.next; //B is the node we want to remove
Node C = B.next; //C is the node right after the node we want to remove
A.next = C;
B.next = null;

}

public String toString()
{
StringBuffer strBuf = new StringBuffer();
Node n = head;
boolean first = true;

while (n != null)
{
int absCoef = n.coeff;

if (!first)
{
if (n.coeff >= 0)
strBuf.append(" + ");
else
{
absCoef = -absCoef;
strBuf.append(" - ");
}
}
strBuf.append(absCoef).append("x^^").append(n.power);
first = false;
n = n.next;
}
return strBuf.toString();

}

public class Node
{
public int coeff;
public int power;
public Node next;

public Node(int coeff, int power, Node next)
{
this.coeff = coeff;
this.power = power;
this.next = next;
}
}

}

//loop though the nodes until we got to the desired index - 1 and keep the reference of the node as A (A is the node right before the node we want to remove)
public void removeNode(int indexnumber)
{
Node n = head;
int i = 0;
while (i < indexnumber - 1){
n = n.next;
if(n.next == null)
//throw exception
++i;
}
Node A = n;
//(if we encounter a node with the next node pointing to null, thow an exception)
Node B = A.next; //B is the node we want to remove
Node C = B.next; //C is the node right after the node we want to remove
A.next = C;
B.next = null;

}

Originally Posted by destin

Right. But what does happen? Is it removing the wrong index? Is an exception being thrown? Is nothing happening? Show some interest and some willingness to think.

Exception in thread "main" java.lang.NullPointerException
at Polynomial.removeNode(Polynomial.java:88)
at PolyTest.main(PolyTest.java:16)

//loop though the nodes until we got to the desired index - 1 and keep the reference of the node as A (A is the node right before the node we want to remove)
public void removeNode(int indexnumber)
{
Node n = head;
for (int i =0; i < indexnumber -1; i++){
n = n.next;
if (n.next == null){
//throw
}
}
Node A = n;
//(if we encounter a node with the next node pointing to null, thow an exception)
Node B = A.next; //B is the node we want to remove
Node C = B.next; //C is the node right after the node we want to remove
A.next = C;
B.next = null;

}

Originally Posted by yawjava

Sir i am new to java so please be patient with me. I get this error

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Exception in thread "main" java.lang.NullPointerException
at Polynomial.removeNode(Polynomial.java:88)
at PolyTest.main(PolyTest.java:16)

Exception in thread "main" java.lang.NullPointerException at Polynomial.removeNode(Polynomial.java:88) at PolyTest.main(PolyTest.java:16)

Node C = B.next; //C is the node right after the node we want to remove