用两个栈实现队列
public class Solution {
Stack<Integer> stack1 = new Stack<Integer>();
Stack<Integer> stack2 = new Stack<Integer>();
public void push(int node) {
stack2.push(node);
}
public int pop() {
if(stack1.isEmpty()){
while (!stack2.isEmpty()){
stack1.push(stack2.pop());
}
}
return stack1.pop();
}
}
