LintCode-12.带最小值操作的栈

public class MinStack {
    private Stack<Integer> data;
    private Stack<Integer> mins;
    public MinStack() {
        // do intialization if necessary
        this.data = new Stack<Integer>();
        this.mins = new Stack<Integer>();
    }

    /*
     * @param number: An integer
     * @return: nothing
     */
    public void push(int number) {
        // write your code here
        data.add(number);
        if(mins.empty() || mins.peek() >= number)
             mins.add(number);
    }

    /*
     * @return: An integer
     */
    public int pop() {
        // write your code here
        int ret = data.pop();
        if(ret == mins.peek())
            mins.pop();
        return ret;
    }

    /*
     * @return: An integer
     */
    public int min() {
        // write your code here
        return mins.peek();
    }
}