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queue_using_stack.java
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queue_using_stack.java
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import java.util.*;
class Qu {
static class Queue {
static Stack<Integer> s1 = new Stack<Integer>();
static Stack<Integer> s2 = new Stack<Integer>();
static void enQueue(int x) {
// Move all elements from s1 to s2
while (!s1.isEmpty()) {
s2.push(s1.pop());
// s1.pop();
}
// Push item into s1
s1.push(x);
// Push everything back to s1
while (!s2.isEmpty()) {
s1.push(s2.pop());
// s2.pop();
}
}
// Dequeue an item from the queue
static int deQueue() {
// if first stack is empty
if (s1.isEmpty()) {
System.out.println("Q is Empty");
System.exit(0);
}
// Return top of s1
int x = s1.peek();
s1.pop();
return x;
}
};
// Driver code
public static void main(String[] args) {
Queue q = new Queue();
q.enQueue(1);
q.enQueue(2);
q.enQueue(3);
System.out.println(q.deQueue());
System.out.println(q.deQueue());
System.out.println(q.deQueue());
}
}