数据结构学习--数组

自定义数组类，实现数组的增删改查

使用java

增加 ：指定位置的，包括后面的元素，统一向后移动，并且size++,如果大小超过容量，就扩容   =>均摊复杂度O(1)

删除:指定位置后面的元素，统一向前移动一格，并且size--,如果大小小于原来容量的1/4.就缩容=>均摊复杂度是O(1)

修改：指定元素修改 O(1)

查询:查询，

package com.zggj.modify.common;

public class Array {
    private int[] data;//存储数据的数组
    private int size;//数组目前有多少个元素


    //构造函数 :根据传入的容量量初始化
    public Array(int capacity) {
        data = new int[capacity];
        size = 0;
    }

    //无参构造函数.默认容量为10
    public Array() {
        this(10);
    }

    //获取size
    public int getSize() {
        return size;
    }

    // 获取数组中的数据容量(最多可以容纳多少元素)
    public int getCapacity() {
        return data.length;
    }

    //判断数组中数据是否为0，直接判断数组的实时大小size即可
    public boolean isEmpty() {
        return size == 0;
    }

    //获取指定位置的元素
    public int get(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        return data[index];
    }

    public int getFirst() {
        return get(0);
    }

    public int getLast() {
        return get(size - 1);
    }


    //判断是否包含指定元素
    public boolean contain(int element) {
        for (int i = 0; i < size; i++) {
            if (data[i] == element) {
                return true;
            }
        }
        return false;
    }

    // 查找指定元素  返回索引
    public int find(int element) {
        for (int i = 0; i < size; i++) {
            if (data[i] == element) {
                return i;
            }
        }
        return -1;
    }

    // 向data中的index位置插入一个元素e
    public void insert(int index, int element) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        //如果容量已满,扩容
        if (size == data.length) {
            resize(data.length * 2);
        }
        // index后面的所有元素后移
        for (int i = size; i > index; i--) {
            data[i] = data[i - 1];
        }
        data[index] = element;
        size++;
    }

    public void addFirst(int element) {
        insert(0, element);
    }

    public void addLast(int element) {
        insert(size, element);
    }


    // 从数组中删除index位置的元素，并返回删除的元素
    public int remove(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        int ret = data[index];//删除的要返回
        if (size < data.length / 4 && data.length / 2 != 0) {
            resize(data.length / 2);
        }
        for (int i = index; i < size; i++) {
            data[i] = data[i + 1];
        }
        size--;
        return ret;
    }

    public int removeFirst() {
        return remove(0);
    }

    public int removeLast() {
        return remove(size - 1);
    }

    //移除指定元素
    public void removeElement(int element) {
        int index = find(element);
        if (index != -1) {//找到，就移除
            remove(index);
        }
    }

    //扩容或者缩容
    public void resize(int capacity) {
        int[] newArr = new int[capacity];
        for (int i = 0; i < size; i++) {
            newArr[i] = data[i];
        }
        data = newArr;
    }

    //更新
    public void set(int index, int element) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        data[index] = element;
    }

    public void setFirst(int element) {
        set(0, element);
    }

    public void setLast(int element) {
        set(size - 1, element);
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append(String.format("Array:size:%d,capacity:%d\n", size, getCapacity()));
        builder.append("[");
        for (int i = 0; i < size; i++) {
            builder.append(data[i] + ",");
        }
        builder.append("]");
        return builder.toString();
    }

    //测试代码的main函数
    public static void main(String[] args) {
        Array array = new Array();
        for (int i = 0; i < array.getCapacity(); i++) {
            array.addLast(i);
            System.out.print(array.toString());
        }
        array.insert(3, 99);
        System.out.print(array.toString());
        array.remove(2);
        System.out.print(array.toString());
        array.removeFirst();
        System.out.print(array.toString());
        array.removeLast();
        System.out.print(array.toString());
    }
}

 使用泛型改写数组

package com.zggj.modify.common;

public class Array<E> {
    private E[] data;//存储数据的数组
    private int size;//数组目前有多少个元素


    //构造函数 :根据传入的容量量初始化
    public Array(int capacity) {
        data = (E[])new Object[capacity];
        size = 0;
    }

    //无参构造函数.默认容量为10
    public Array() {
        this(10);
    }

    //获取size
    public int getSize() {
        return size;
    }

    // 获取数组中的数据容量(最多可以容纳多少元素)
    public int getCapacity() {
        return data.length;
    }

    //判断数组中数据是否为0，直接判断数组的实时大小size即可
    public boolean isEmpty() {
        return size == 0;
    }

    //获取指定位置的元素
    public E get(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        return data[index];
    }

    public E getFirst() {
        return get(0);
    }

    public E getLast() {
        return get(size - 1);
    }


    //判断是否包含指定元素
    public boolean contain(E element) {
        for (int i = 0; i < size; i++) {
            if (data[i] == element) {
                return true;
            }
        }
        return false;
    }

    // 查找指定元素  返回索引
    public int find(E element) {
        for (int i = 0; i < size; i++) {
            if (data[i] == element) {
                return i;
            }
        }
        return -1;
    }

    // 向data中的index位置插入一个元素e
    public void insert(int index, E element) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        //如果容量已满,扩容
        if (size == data.length) {
            resize(data.length * 2);
        }
        // index后面的所有元素后移
        for (int i = size; i > index; i--) {
            data[i] = data[i - 1];
        }
        data[index] = element;
        size++;
    }

    public void addFirst(E element) {
        insert(0, element);
    }

    public void addLast(E element) {
        insert(size, element);
    }


    // 从数组中删除index位置的元素，并返回删除的元素
    public E remove(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        E ret = data[index];//删除的要返回
        if (size < data.length / 4 && data.length / 2 != 0) {
            resize(data.length / 2);
        }
        for (int i = index; i < size; i++) {
            data[i] = data[i + 1];
        }
        size--;
        return ret;
    }

    public E removeFirst() {
        return remove(0);
    }

    public E removeLast() {
        return remove(size - 1);
    }

    //移除指定元素
    public void removeElement(E element) {
        int index = find(element);
        if (index != -1) {//找到，就移除
            remove(index);
        }
    }

    //扩容或者缩容
    public void resize(int capacity) {
        E[] newArr = (E[])new Object[capacity];
        for (int i = 0; i < size; i++) {
            newArr[i] = data[i];
        }
        data = newArr;
    }

    //更新
    public void set(int index, E element) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("插入元素失败！index的范围必须在[0, size)");
        }
        data[index] = element;
    }

    public void setFirst(E element) {
        set(0, element);
    }

    public void setLast(E element) {
        set(size - 1, element);
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append(String.format("Array:size:%d,capacity:%d\n", size, getCapacity()));
        builder.append("[");
        for (int i = 0; i < size; i++) {
            builder.append(data[i] + ",");
        }
        builder.append("]");
        return builder.toString();
    }

    //测试代码的main函数
    public static void main(String[] args) {
        Array<Integer> array = new Array<Integer>();
        for (int i = 0; i < array.getCapacity(); i++) {
            array.addLast(i);
            System.out.print(array.toString());
        }
        array.insert(3, 99);
        System.out.print(array.toString());
        array.remove(2);
        System.out.print(array.toString());
        array.removeFirst();
        System.out.print(array.toString());
        array.removeLast();
        System.out.print(array.toString());
    }
}