方法1：
import java.util.Stack;
public class Solution {
Stack<Integer> stack1 = new Stack<Integer>();
Stack<Integer> stack2 = new Stack<Integer>();
public void push(int node) {
stack1.push(node);
}
public int pop() {
if(stack1.isEmpty() && stack2.isEmpty()){
throw new RuntimeException("栈为空");
}
if(stack2.isEmpty()){
while(!stack1.isEmpty()){
stack2.push(stack1.pop());
}
}
return stack2.pop();
}
}
方法2：
import java.util.Stack;
public class Solution {
Stack<Integer> stack1 = new Stack<Integer>();
Stack<Integer> stack2 = new Stack<Integer>();
public void push(int node) {
stack1.push(node);
}
public int pop() {
while(!stack1.isEmpty()){
stack2.push(stack1.pop());
}
int out = stack2.pop();
while(!stack2.isEmpty()){
stack1.push(stack2.pop());
}
return out;
}
}
