Question

You may not use the java.util.Stack class.
You may not use the java.util.Queue class.

Write a method public static void removeDownTo (long n): It pops all values off the stack down to but not including the first element it sees that is equal to the second parameter. If none are equal, leave the stack empty.

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// stack.java
// demonstrates stacks
////////////////////////////////////////////////////////////////
class StackX
{
private int maxSize; // size of stack array
private long[] stackArray;
private int top; // top of stack
//--------------------------------------------------------------
public StackX(int s) // constructor
{
maxSize = s; // set array size
stackArray = new long[maxSize]; // create array
top = -1; // no items yet
}
//--------------------------------------------------------------
public void push(long j) // put item on top of stack
{
stackArray[++top] = j; // increment top, insert item
}
//--------------------------------------------------------------
public long pop() // take item from top of stack
{
return stackArray[top--]; // access item, decrement top
}
//--------------------------------------------------------------
public long peek() // peek at top of stack
{
return stackArray[top];
}
//--------------------------------------------------------------
public boolean isEmpty() // true if stack is empty
{
return (top == -1);
}
//--------------------------------------------------------------
public boolean isFull() // true if stack is full
{
return (top == maxSize-1);
}
//--------------------------------------------------------------
} // end class StackX
////////////////////////////////////////////////////////////////
class StackApp
{
public static void main(String[] args)
{
StackX theStack = new StackX(10); // make new stack
theStack.push(20); // push items onto stack
theStack.push(40);
theStack.push(60);
theStack.push(80);

while( !theStack.isEmpty() ) // until it's empty,
{ // delete item from stack
long value = theStack.pop();
System.out.print(value); // display it
System.out.print(" ");
} // end while
System.out.println("");
} // end main()
} // end class StackApp
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
ONLY FOR TESTING CODE, DO NOT CHANGE ANYTHING IN STACKTEST.JAVA

public class StackTest
{
    public static void main(String[] args)
    {
        StackX theStack = new StackX(10);  // make new stack
        theStack.push(20);               // push items onto stack
        theStack.push(30);
        theStack.push(40);
        theStack.push(40);
        theStack.push(60);
        theStack.push(80);

        theStack.showStack();

        System.out.println("removeDownTo(40)");
        theStack.removeDownTo(40);

        theStack.showStack();

    }  // end main()
}

Answer 1

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class StackX
{
private int maxSize; // size of stack array
private long[] stackArray;
private int top; // top of stack
//--------------------------------------------------------------
public StackX(int s) // constructor
{
maxSize = s; // set array size
stackArray = new long[maxSize]; // create array
top = -1; // no items yet
}
//--------------------------------------------------------------
public void push(long j) // put item on top of stack
{
stackArray[++top] = j; // increment top, insert item
}
//--------------------------------------------------------------
public long pop() // take item from top of stack
{
return stackArray[top--]; // access item, decrement top
}
//--------------------------------------------------------------
public long peek() // peek at top of stack
{
return stackArray[top];
}
//--------------------------------------------------------------
public boolean isEmpty() // true if stack is empty
{
return (top == -1);
}
//--------------------------------------------------------------
public boolean isFull() // true if stack is full
{
return (top == maxSize-1);
}
//--------------------------------------------------------------
public void removeDownTo(long number){
// intially check wether the stack is empty before removing any element
if(!this.isEmpty()){
// now pop till the element looking for is found
while(!this.isEmpty() && stackArray[top]!=number){
top--;
}
}else{
System.out.println("stock is empty");
}
}
public void showStack(){
// this method is used to show the element of stack as you called this method from main
// you didn't ask to write but for testing i have written down
// if dont require this method comment it down
int index = top;
while(index>=0){
System.out.println(stackArray[index]);
index--;
}
}
} // end class StackX
////////////////////////////////////////////////////////////////
class StackApp
{
public static void main(String[] args)
{
StackX theStack = new StackX(10); // make new stack
theStack.push(20); // push items onto stack
theStack.push(40);
theStack.push(60);
theStack.push(80);

while( !theStack.isEmpty() ) // until it's empty,
{ // delete item from stack
long value = theStack.pop();
System.out.print(value); // display it
System.out.print(" ");
} // end while
System.out.println("");
} // end main()
} // end class StackApp
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

public class Main
{
public static void main(String[] args)
{
StackX theStack = new StackX(10); // make new stack
theStack.push(20); // push items onto stack
theStack.push(30);
theStack.push(40);
theStack.push(40);
theStack.push(60);
theStack.push(80);

theStack.showStack();

System.out.println("removeDownTo(40)");
theStack.removeDownTo(40);

theStack.showStack();

} // end main()
}