代码随想录算法训练营第九天-232用栈实现队列、225用队列实现栈

前言
状态：都是直接看的解析，不是很难。
更新

        
24.05.30 初始记录

初步题解

232 用栈实现队列

题目链接：(https://leetcode.cn/problems/implement-queue-using-stacks/description/)

        JAVA
        
      
public class LE232 {  
    public static void main(String[] args) {  
        MyQueue queue = new MyQueue();  
        queue.push(1);  
        queue.push(2);  
        System.out.println("queue.peek() = " + queue.peek());  
        System.out.println("queue.pop() = " + queue.pop());  
        System.out.println("queue.empty() = " + queue.empty());  
    }  
  
    static class MyQueue {  
        Stack<Integer> stackIn;  
        Stack<Integer> stackOut;  
  
        public MyQueue() {  
            stackIn = new Stack<>();  
            stackOut = new Stack<>();  
        }  
  
        public void push(int x) {  
            stackIn.push(x);  
        }  
  
        public int pop() {  
            // 把in的内容复制到out  
            in2out();  
            return stackOut.pop();  
        }  
  
        private void in2out() {  
            if (stackOut.isEmpty()) {  
                while (!stackIn.isEmpty()) {  
                    stackOut.push(stackIn.pop());  
                }  
            }  
        }  
  
        /**  
         * 返回列表开头的数据  
         * @return 结果  
         */  
        public int peek() {  
            // 把in的内容复制到out  
            in2out();  
            return stackOut.peek();  
        }  
  
        public boolean empty() {  
            return stackIn.empty() && stackOut.empty();  
        }  
    }  
}

225 用队列实现栈

题目链接：(https://leetcode.cn/problems/implement-queue-using-stacks/description/)

        JAVA
        
      
public class LE225 {  
    public static void main(String[] args) {  
        MyStack myStack = new MyStack();  
        myStack.push(1);  
        myStack.push(2);  
        System.out.println("myStack.top() = " + myStack.top());  
        System.out.println("myStack.pop() = " + myStack.pop());  
        System.out.println("myStack.empty() = " + myStack.empty());  
    }  
  
    static class MyStack {  
        Queue<Integer> queue;  
  
        public MyStack() {  
            queue = new LinkedList<>();  
        }  
  
        public void push(int x) {  
            queue.offer(x);  
            int size = queue.size() - 1;  
            while (size != 0) {  
                size--;  
                queue.offer(queue.poll());  
            }  
        }  
  
        public int pop() {  
            return queue.poll();  
        }  
  
        public int top() {  
            return queue.peek();  
        }  
  
        /**  
         * 判断是否为空  
         */  
        public boolean empty() {  
            return queue.isEmpty();  
        }  
    }  
}