用数组结构实现大小固定的队列和栈

用数组结构实现大小固定的队列和栈

1. 队列

可以通过 start 和 end两个指针来控制队列的进出，通过设置size来简化判断队列状态。需要注意 nextIndex 方法，指针可以循环的在数组中跑起来，不许要担心数组指针位置问题。

class ArrayQueue {
    private static int size;
    private static int start;
    private static int end;
    private static int[] nums;

    public ArrayQueue(int length) {
        this.nums = new int[length];
    }

    public int get() {
        if (!isEmpty()){
            size--;
            int num = nums[start];
            start=nextIndex(start);
            return num;
        }else{
            return -1;
        }
    }

    public void put(int element) {
        if (!isFull()) {
            nums[end] = element;
            end = nextIndex(end);
            size++;
        }
    }

    public boolean isFull() {
        if (size == nums.length) {
            System.out.println("QUEUE IS FULL");
            return true;
        } else {
            return false;
        }
    }

    public boolean isEmpty() {
        if (size == 0) {
            System.out.println("QUEUE IS EMPTY");
            return true;
        } else {
            return false;
        }
    }

    private int nextIndex(int index){
        if (index == nums.length-1){
            return 0;
        }else{
            return ++index;
        }
    }

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder("start\t");
        int key = start;
        for (int i=0;i<size;i++){
            stringBuilder.append(nums[key]+"\t");
            key = nextIndex(key);
        }
        stringBuilder.append("end\t");
        return stringBuilder.toString();
    }
}

2. 栈

利用一个指针就可以是实现栈的压入和弹出。

class ArrayStack{
    static int size = 0 ;
    static int[] array ;
    static int point = 0;

    public ArrayStack(int lengh) {
        this.array = new int[lengh];
    }

    public static int peek(){
        if (isEmpty()){
            return -1;
        }
        return array[point-1];
    }

    public static int pop(){
        if (isEmpty()){
            return -1;
        }
        size--;
        return array[--point];
    }

    public static void push(int element){
        if (isFull()){
            return;
        }
        array[point++] = element;
        size++;
    }

    public static boolean isEmpty(){
        return size==0;
    }

    public static boolean isFull(){
        if (size==array.length){
            System.out.println("Stack is full");
            return true;
        }else{
            return false;
        }
    }

    public String toString(){
        StringBuilder builder = new StringBuilder("[");
        for (int i=0;i<size;i++){
            builder.append(array[i]+"\t");
        }
        builder.append("]");
        return builder.toString();
    }
}