数据结构之动态数组

数据结构

属性

• private E[] data
• private int size;

接口列表

• public Array(int capacity)
• public Array()
• public int getCapacity()
• public int getSize()
• public boolean isEmpty()
• public void addLast(E e)
• public void addFirst(E e)
• public void add(int index, E e)
• public E get(int index)
• public E getFirst()
• public E getLast()
• public void set(int index, E e)
• public boolean contains(E e)
• public int find(E e)
• public E removeLast()
• public E removeFirst()
• public E remove(int index)
• public void removeElement(E e)
• private void resize(int newCapacity)
• public String toString()

代码示例

public class Array<E> {
    private E[] data;
    private int size;
    /**
     * 构造函数，传入数组的容量capacity构造Array
     * @param capacity
     */
    public Array(int capacity) {
        this.data = (E[])new Object[capacity];
        this.size = 0;
    }
    /**
     * 无参数的构造函数，默认数组的容量capacity=10
     */
    public Array() {
        this(10);
    }
    /**
     * 获取数组的容量
     * @return
     */
    public int getCapacity() {
        return this.data.length;
    }
    /**
     * 获取数组中的元素个数
     * @return
     */
    public int getSize() {
        return this.size;
    }
    /**
     * 返回数组是否为空
     * @return
     */
    public boolean isEmpty() {
        return this.size == 0;
    }
    /**
     * 在index索引的位置插入一个新元素e
     * @param index
     * @param e
     */
    public void add(int index, E e) {
        if (index < 0 || index > this.size) {
            throw new IllegalArgumentException("Add failed. Required index >= 0 and index <= size");
        }
        if (this.size == this.data.length) {
            resize(this.data.length * 2);
        }
        for (int i = this.size - 1; i >= index; i--) {
            this.data[i + 1] = this.data[i];
        }
        this.data[index] = e;
        this.size ++;
    }
    /**
     * 向所有元素后添加一个新元素
     * @param e
     */
    public void addLast(E e) {
        this.add(this.size, e);
    }
    /**
     * 在所有元素前添加一个新元素
     * @param e
     */
    public void addFirst(E e) {
        this.add(0, e);
    }
    /**
     * 获取index索引位置的元素
     * @param index
     * @return
     */
    public E get(int index) {
        if (index < 0 || index >= this.size) {
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        }
        return this.data[index];
    }
    /**
     * 获取第一个元素
     * @return
     */
    public E getFirst() {
        return this.get(0);
    }
    /**
     * 获取最后一个元素
     * @return
     */
    public E getLast() {
        return this.get(this.size - 1);
    }
    /**
     * 修改index索引位置的元素为e
     * @param index
     * @param e
     */
    public void set(int index, E e) {
        if (index < 0 || index >= this.size) {
            throw new IllegalArgumentException("Set failed. Index is illegal.");
        }
        this.data[index] = e;
    }
    /**
     * 查找数组中是否有元素e
     * @param e
     * @return
     */
    public boolean contains(E e) {
        for (int i = 0; i < this.size; i++) {
            if (this.data[i].equals(e)) {
                return true;
            }
        }
        return false;
    }
    /**
     * 查找数组中元素e所在的索引，如果不存在元素e，则返回-1
     * @param e
     * @return
     */
    public int find(E e) {
        for (int i = 0; i < this.size; i++) {
            if (this.data[i].equals(e)) {
                return i;
            }
        }
        return -1;
    }
    /**
     * 从数组中删除index位置的元素, 返回删除的元素
     * @param index
     * @return
     */
    public E remove(int index) {
        if (index < 0 || index >= this.size) {
            throw new IllegalArgumentException("Remove failed. Index is illegal.");
        }
        E ret = this.data[index];
        for (int i = index + 1; i < this.size; i++) {
            this.data[i - 1] = this.data[i];
        }
        this.size --;
        this.data[this.size] = null;
        if (this.size == this.data.length / 4 && this.data.length / 2 != 0) {
            resize(this.data.length / 2);
        }
        return ret;
    }
    /**
     * 从数组中删除第一个元素, 返回删除的元素
     * @return
     */
    public E removeFirst() {
        return this.remove(0);
    }
    /**
     * 从数组中删除最后一个元素, 返回删除的元素
     * @return
     */
    public E removeLast() {
        return this.remove(this.size - 1);
    }
    /**
     * 从数组中删除元素e
     * @param e
     */
    public void removeElement(E e) {
        int index = this.find(e);
        if (index != -1) {
            this.remove(index);
        }
    }
    /**
     * 交换位置i,j的元素
     * @param i
     * @param j
     */
    public void swap(int i, int j) {
        if (i < 0 || i >= this.size || j < 0 || j >= this.size) {
            throw new IllegalArgumentException("Swap failed. Index is illegal.");
        }
        E tmp = this.data[i];
        this.data[i] = this.data[j];
        this.data[j] = tmp;
    }
    /**
     * 将数组空间的容量变成newCapacity大小
     * @param newCapacity
     */
    private void resize(int newCapacity) {
        E[] newData = (E[])new Object[newCapacity];
        for (int i = 0; i < this.size; i++) {
            newData[i] = this.data[i];
        }
        this.data = newData;
    }
    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array: size = %d, capacity = %d\n", this.size, this.data.length));
        res.append('[');
        for (int i = 0; i < this.size; i++) {
            res.append(this.data[i]);
            if (i != this.size - 1) {
                res.append(", ");
            }
        }
        res.append(']');
        return res.toString();
    }
}