Sword Finger Offer-1.15-09

class CQueue {
    
    
    private Stack<Integer> in;
    private Stack<Integer> out;

    public CQueue() {
    
    
        in = new Stack<Integer>();
        out = new Stack<Integer>();
    }
    
    public void appendTail(int value) {
    
    
        in.push(value);
    }
    
    public int deleteHead() {
    
    
        if (!out.isEmpty()) {
    
    
            return out.pop();
        } else {
    
    
            while (!in.isEmpty()) {
    
    
                out.push(in.pop());
            }
            return out.isEmpty() ? -1 : out.pop();
        }
    }
}

/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue obj = new CQueue();
 * obj.appendTail(value);
 * int param_2 = obj.deleteHead();
 */