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Stack_Queue.java
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Stack_Queue.java
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import java.util.LinkedList;
import java.util.Queue;
public class Stack_Queue {
public static class Stack {
//2 queues
Queue<String> q1 = new LinkedList<String>();
Queue<String> q2 = new LinkedList<String>();
public int curr_size;
Stack()
{
curr_size = 0;
}
void push(String x)
{
curr_size++;
// Push x first in empty q2
q2.add(x);
// Push all q1 to q2
while (!q1.isEmpty()) {
q2.add(q1.peek());
q1.remove();
}
Queue<String> q = q1;
q1 = q2; //copy all q2 to q1
q2 = q; //empty q2
}
public void pop()
{
// if no elements are there in q1
if (q1.isEmpty()) {
return;
}
q1.remove();
curr_size--;
}
public String lastElement()
{
if (q1.isEmpty()){
return "Empty";
}
return q1.peek();
}
public int size()
{
return curr_size;
}
}
}