Question

JAVA language

Add a recursive method to the program shown in the previous section that states
how many times a particular value appears on the stack.

Code:

class Stack {

protected Node top;

Stack() {

top = null; }

boolean isEmpty() {

return( top == null); }

void push(int v) {

Node tempPointer;

tempPointer = new Node(v);

tempPointer.nextNode = top;

top = tempPointer; }

int pop() {

int tempValue;

tempValue = top.value;

top = top.nextNode;

return tempValue; }

void printStack() {

Node aPointer = top;

String tempString = "";

while (aPointer != null) {

tempString = tempString + aPointer.value + "\n";

aPointer = aPointer.nextNode; }

System.out.println(tempString); }

boolean hasValue(int v) {

if (top.value == v) {

return true; }

else {

return hasValueSubList(top,v);

}

}

boolean hasValueSubList(Node ptr, int v) {

if (ptr.nextNode == null) {

return false; }

else if (ptr.nextNode.value == v) {

return true; }

else {

return hasValueSubList(ptr.nextNode,v);

}

}

}

class Node {

int value;

Node nextNode;

Node(int v, Node n) {

value = v;

nextNode = n;

}

Node (int v) {

this(v,null);

}

}

public class StackWithLinkedList2{

public static void main(String[] args){

int popValue;

Stack myStack = new Stack();

myStack.push(5);

myStack.push(7);

myStack.push(9);

System.out.println(myStack.hasValue(11));

}

}

Answer 1

PROGRAM :

class Stack {
protected Node top;

Stack() {
top = null;
}

boolean isEmpty() {
return (top == null);
}

void push(int v) {
Node tempPointer;
tempPointer = new Node(v);
tempPointer.nextNode = top;
top = tempPointer;
}

int pop() {
int tempValue;
tempValue = top.value;
top = top.nextNode;
return tempValue;
}

void printStack() {
Node aPointer = top;
String tempString = "";
while (aPointer != null) {
tempString = tempString + aPointer.value + "\n";
aPointer = aPointer.nextNode;
}
System.out.println(tempString);
}

boolean hasValue(int v) {
if (top.value == v) {
return true;
} else {
return hasValueSubList(top, v);
}
}

boolean hasValueSubList(Node ptr, int v) {
if (ptr.nextNode == null) {
return false;
} else if (ptr.nextNode.value == v) {
return true;
} else {
return hasValueSubList(ptr.nextNode, v);
}
}

// method to insert a value at the end of the stack
void insertEnd(int v) {
// if stack is empty, adding v as the top node
if (isEmpty()) {
top = new Node(v);
} else {
// else, calling the private recursive method, passing top node and
// v
insertEnd(top, v);
}
}

// private helper method to assist the above method. this is where the
// actual recursion takes place
private void insertEnd(Node n, int v) {
// if n is the last node (no next node), adding a new node after n, with
// value v
if (n.nextNode == null) {
n.nextNode = new Node(v);
} else {
// otherwise calling method recursively, passing next node
insertEnd(n.nextNode, v);
}
}
}

class Node {
int value;
Node nextNode;

Node(int v, Node n) {
value = v;
nextNode = n;
}

Node(int v) {
this(v, null);
}
}

public class StackWithLinkedList2 {
public static void main(String[] args) {
int popValue;
Stack myStack = new Stack();
myStack.push(5);
myStack.push(7);
myStack.push(9);
// printing stack
myStack.printStack();
// adding 11 to the end
myStack.insertEnd(11);
// printing stack again
myStack.printStack();
}
}

OUTPUT :

9
7
5

9
7
5
11