Coding Exercises Day 24 (Problem #17)

Problem:

Implement a MyQueue class which implements a queue using two stacks.

class MyQueue {
  Stack<Node> stackLIFO = new Stack<Node>(); 
  Stack<Node> stackFIFO = new Stack<Node>();
  
  public void enqueue(Node node) {
    stackLIFO.push(node);
  }

  public Node dequeue() {
    if (stackFIFO.isEmpty() && stackLIFO.isEmpty()) return null;

    if (!stackFIFO.isEmpty()) {
      return stackFIFO.pop();
    }
    else {
      while(!stackLIFO.isEmpty()) {
        Node temp = stackLIFO.pop();
        stackFIFO.push(temp);
      }
      return stackFIFO.pop();
    }
  }
}