模拟一个arraylist, 就是 FI LO
public class Stack { /* * @param x: An integer * @return: nothing */ private Listlist = new ArrayList<>();
public void push(int x) {
// write your code here
list.add(x);
}
/*
* @return: nothing
*/
public void pop() {
// write your code here
list.remove(list.size() - 1);
}
/*
* @return: An integer
*/
public int top() {
// write your code here
return list.get(list.size() - 1);
}
/*
* @return: True if the stack is empty
*/
public boolean isEmpty() {
// write your code here
return list.size() <= 0;
}
}
