Java数据结构的实现

1.基于数组的链表

package array;

import java.util.Arrays;

/**
 * 基于数组的链表
 * 
 * @author 王彪
 *
 */
public class MyArrayList {
    private static Object[] elements = null;
    private static int size = 0;
    private static final int DEFUAT_INITIAL_CAPACITY = 10;

    public MyArrayList() {
        this(10);
    }

    public MyArrayList(int initialCapacity) {
        if (initialCapacity < 0) {
            throw new IllegalArgumentException("输入容量有误");
        }
        elements = new Object[initialCapacity];
    }

//初始化数组
    // 保存新元素
    public void add(Object ele) {
        // 数组的扩容问题
        if (size == elements.length) {
            Object[] temp = Arrays.copyOf(elements, elements.length * 2);
            elements = temp;
        }
        elements[size] = ele;
        size++;
    }

    public Object get(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("输入索引有误");
        }
        return elements[index];
    }

    public void set(int index, Object newPlayerNum) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("输入索引有误");
        }
        elements[index] = newPlayerNum;
    }

    public void remove(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("输入索引有误");
        }
        for (int i = index; i < size - 1; i++) {
            elements[i] = elements[i + 1];
        }
        elements[size - 1] = null;
        size--;
    }

    public String toString() {
        if (elements == null) {
            return null;
        }
        if (size == 0) {
            return "[]";
        }
        StringBuilder sb = new StringBuilder(size * 3 + 1);
        sb.append("[");
        for (int i = 0; i < size; i++) {
            sb.append(elements[i]);
            if (i < size - 1) {
                sb.append(",");
            }
            if (i == size - 1) {
                sb.append("]");
            }
        }
        return sb.toString();
    }

    public int size() {
        return size;
    }

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

    public void clear() {
        this.elements = new Object[DEFUAT_INITIAL_CAPACITY];
        size = 0;
    }

}

---

2.双向链表

package linked;

public class MyLinkedArrayList {
    protected Node first;
    protected Node last;
    protected int size;

    public void addFirst(Object ele) {// 在头部增加
        Node node = new Node(ele);
        if (size == 0) {
            this.first = node;
            this.last = node;
        } else {
            node.next = this.first;
            this.first.prev = node;
            this.first = node;
        }
        size++;
    }

    public void addLast(Object ele) {// 在尾部增加
        Node node = new Node(ele);
        if (size == 0) {
            this.first = node;
            this.last = node;
        } else {
            this.last.next = node;
            node.prev = this.last;
            this.last = node;
        }
        size++;
    }

    public void remove(Object ele) {
        Node current = this.first;
        for (int i = 0; i < size; i++) {
            if (!current.ele.equals(ele)) {
                if (current.next == null) {
                    return;
                }
                current = current.next;
            }
        }
        if (current == this.first) {
            this.first = current.next;
            this.first.prev = null;
        } else if (current == this.last) {
            this.last = current.prev;
            this.last.next = null;
        } else {
            current.prev.next = current.next;
            current.next.prev = current.prev;
        }
        size--;
    }

    @Override
    public String toString() {
        if (size == 0) {
            return "[]";
        } else {
            StringBuilder sb = new StringBuilder(size * 3 + 1);
            Node current = this.first;// 第一个节点
            sb.append("[");
            for (int i = 0; i < size; i++) {
                sb.append(current.ele);
                if (i != size - 1) {
                    sb.append(",");
                } else {
                    sb.append("]");
                }
                current = current.next;
            }
            return sb.toString();
        }
    }

    public class Node {
        public Node(Object ele) {
            this.ele = ele;
        }

        Node prev;
        Node next;
        public Object ele;
    }
}

---

3.双向队列

package deque;

import linked.MyLinkedArrayList;

public class MyDeque extends MyLinkedArrayList {
    public Object getFirst() {
        return this.first.ele;
    }

    public Object getLast() {
        return this.last.ele;
    }

    public void removeFirst(Object ele) {
        super.remove(this.first);
    }

    public void removeLast(Object ele) {
        super.remove(this.last);
    }

    public void addFirst(Object ele) {
        super.addFirst(ele);
    }

    public void addLast(Object ele) {
        super.addLast(ele);
    }

}

---

4.堆

package stack;

import array.MyArrayList;

//栈
public class MyStack extends MyArrayList {
    // 入栈
    public void push(Object ele) {
        super.add(ele);
    }

    // 删除栈顶元素
    public void pop() {
        int index = super.size() - 1;
        super.remove(index);
    }

    // 查询栈顶元素
    public Object peek() {
        int index = super.size() - 1;
        return super.get(index);
    }

}