Reverse a stack

#1

for(int i=0;i<o.SizeofStack();i++)
{
h.Push(o.Pop());
}
h.Display();
this loop is working only 3 times for 50=>40=>30=>20=>10=>END this input of o.

#2

Hi @Kapsime_S,
This loop will work for sizeofstack/2 times. This is because, every time you pop an element the sizeofstack will decrease by 1 and i is incremented by +1 every time it completes a block of code. You can store the sizeofstack in a variable before the for loop. Your code should work after that.

#3

I tried doing that but the result is still same.
int k=o.SizeofStack(); added this before loop.
recursive method is also not working because of this.

#4

@Kapsime_S can you please share your code as well? Thanks

#5

public class Reverse_Stack {

public static void ReverseStack(usingArrays o,usingArrays h,int idx) throws Exception
    {
        int k=o.SizeofStack();
         for(int i=0;i<o.SizeofStack();i++)
        {
            h.Push(o.Pop());
        }
         h.Display();
        
         //RECURSIVE METHOD

// if(o.isEmpty()==true)
// return;
// o.Display();
// int item=o.Pop();
//
// ReverseStack(o, h, idx+1);
// h.Push(item);
//
// if(idx==0)
// {
// while(!h.isEmpty())
// {
// o.Push(h.Pop());
// }
// }
//
}

public static void main(String[] args) throws Exception {
    
    usingArrays Original =new usingArrays(5);
    usingArrays Helper =new usingArrays(5);
    
    for(int i=0;i<5;i++)
    {
        Original.Push((i+1)*10);
    }
    System.out.print("ORIGINAL STACK: ");
    Original.Display();
    
    System.out.print("AFTER REVERSING:");
    ReverseStack(Original,Helper,0);

       
}

}

#6

Hey @Kapsime_S,
Try to share your complete code also, in the code snippet given below:
int k=o.SizeofStack();
for(int i=0;i<o.SizeofStack();i++)
{
h.Push(o.Pop());
}
you need to write it as i<k instead i<o.SizeofStack(), because to avoid i being compared to a dynamic value we are storing it in variable k.

#7

package stacks;

public class Reverse_Stack {

public static void ReverseStack(usingArrays o,usingArrays h,int idx) throws Exception
    {
        int k=o.SizeofStack();
        
         for(int i=0;i<k;i++)
        {
            h.Push(o.Pop());
        }
         h.Display();
                 
    }
    
public static void main(String[] args) throws Exception {
    
    usingArrays Original =new usingArrays(5);
    usingArrays Helper =new usingArrays(5);
    
    for(int i=0;i<5;i++)
    {
        Original.Push((i+1)*10);
    }
    System.out.print("ORIGINAL STACK: ");
    Original.Display();
    
    System.out.print("AFTER REVERSING:");
    ReverseStack(Original,Helper,0);

       
}

}
this is full code.
and the error msg.
ORIGINAL STACK: 50=>40=>30=>20=>10=>END
Exception in thread “main” java.lang.Exception: STACK IS EMPTY
at stacks.usingArrays.Pop(usingArrays.java:47)
at stacks.Reverse_Stack.ReverseStack(Reverse_Stack.java:12)
at stacks.Reverse_Stack.main(Reverse_Stack.java:31)
AFTER REVERSING:C:\Users\DELL\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

#8

h.Push(o.Pop());
something is wrong in this line. in recursive method also this line is giving error

#9

Hey @Kapsime_S,
There might be some problem with your pop function because this should work. Anyways, implement it using a while loop.
while(o.SizeofStack()!=0)
{
h.Push(o.Pop());
}
Try this approach and see what the answer you are getting.

#10

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