Java 栈与队列实战真题训练

class MyCircularQueue {
    public int front;
    public int rear;
    public int[] array;
 
    //构造方法
    public MyCircularQueue(int k) {
       //因为预留位置的缘故，数组的大小要定义为k+1
       this.array=new int[k+1];
    }
    //入队
    public boolean enQueue(int value) {
        if(isFull()){
            return false;
        }
        this.array[this.rear]=value;
        this.rear=(this.rear+1)%this.array.length;
        return true;
    }
    //出队
    public boolean deQueue() {
        if(isEmpty()){
            return false;
        }
        this.front=(this.front+1)%this.array.length;
        return true;
    }
    //获取队头
    public int Front() {
        if(isEmpty()){
            return -1;
        }
        return this.array[front];
    }
    //获取队尾
    public int Rear() {
        if(isEmpty()){
            return -1;
        }
        int index=-1;
        if(this.rear==0){
            index=this.array.length-1;
        }else{
            index=this.rear-1;
        }
        return this.array[index];
    }
    //判断是否为空
    public boolean isEmpty() {
        if(this.front==this.rear){
            return true;
        }
        return false;
    }
    //判断队列是否满
    public boolean isFull() {
        if((this.rear+1)%this.array.length==this.front){
            return true;
        }
        return false;
    }
}

class MyStack {
    private Queue<Integer> queue1;
    private Queue<Integer> queue2;
 
    //构造方法
    public MyStack() {
        queue1=new LinkedList<>();
        queue2=new LinkedList<>();
    }
    //入栈
    public void push(int x) {
        if(!queue2.isEmpty()){
            queue2.offer(x);
        }else{
            queue1.offer(x);
        }
    }
    //出栈
    public int pop() {
        if(empty()){
            return -1;
        }
        if(queue1.isEmpty()){
            int size=queue2.size();
            for(int i=0;i<size-1;++i){
                int x=queue2.poll();
                queue1.offer(x);
            }
            return queue2.poll();
        }else{
            int size=queue1.size();
            for(int i=0;i<size-1;++i){
                int x=queue1.poll();
                queue2.offer(x);
            }
            return queue1.poll();
        }
    }
    //获取栈顶元素
    public int top() {
        if(empty()){
            return -1;
        }
        if(queue1.isEmpty()){
            int x=-1;
            int size=queue2.size();
            for(int i=0;i<size;++i){
                x=queue2.poll();
                queue1.offer(x);
            }
           return x;
        }else{
            int size=queue1.size();
            int x=-1;
            for(int i=0;i<size;++i){
                x=queue1.poll();
                queue2.offer(x);
            }
            return x;
        }
    }
    //判断栈是否为空
    public boolean empty() {
        if(queue1.isEmpty()&&queue2.isEmpty()){
            return true;
        }
        return false;
    }
}

class MyQueue {
    private Stack<Integer> stack1;
    private Stack<Integer> stack2;
    //构造方法
    public MyQueue() {
        stack1=new Stack<>();
        stack2=new Stack<>();
    }
    //入队操作
    public void push(int x) {
        stack1.push(x);
    }
    //出队操作
    public int pop() {
        if(stack2.empty()){
            int size=stack1.size();
            for(int i=0;i<size;++i){
                int x=stack1.pop();
                stack2.push(x);
            }
        }
        return stack2.pop();
 
    }
    //获取队列开头的元素
    public int peek() {
        if(stack2.empty()){
            int size=stack1.size();
            for(int i=0;i<size;++i){
                int x=stack1.pop();
                stack2.push(x);
            }
        }
        return stack2.peek();
    }
    //判断队列是否为空
    public boolean empty() {
        if(stack1.empty()&&stack2.empty()){
            return true;
        }
        return false;
    }
}

class MinStack {
    private Stack<Integer> stack1;
    private Stack<Integer> stack2;
    //构造方法
    public MinStack() {
        stack1=new Stack<>();
        stack2=new Stack<>();
    }
    //入栈
    public void push(int val) {
        stack1.push(val);
        if(stack2.empty()){
            stack2.push(val);
        }else{
            if(val<=stack2.peek()){
                stack2.push(val);
            }
        }
    }
    //出栈
    public void pop() {
        int x=stack1.pop();
        if(x==stack2.peek()){
            stack2.pop();
        }
    }
    //获取栈顶元素
    public int top() {
        return stack1.peek();
    }
    //获取栈的最小元素
    public int getMin() {
        return stack2.peek();
    }
}