数据结构之不要小瞧数组

数组基础:

 

 

 

 

 

 

 

 

 

二次封装属于自己的数组

package com.practice.Array;

public class Array {

    private int[] data;
    private int size;

    //构造函数,传入数组的容量capacity构造Array
    public Array(int capacity){
        data = new int[capacity];
        size = 0;
    }

    //无参数的构造函数,默认数组的容量capacity为10
    public Array(){
        this(10);
    }

    //获取数组中的元素个数
    public int getSize(){
        return size;
    }

    //获取数组的容量
    public int getCapacity(){
        return data.length;
    }

    //返回数组是否为空
    public boolean isEmpty(){
        return size == 0;
    }

    //向所有元素后添加一个新的元素
    public void addLast(int e) {

        /*if(size == data.length)
            throw new IllegalArgumentException("AddLast failed.Array is full.");
        data[size] = e;
        size ++;*/
        add(size,e);
    }

    //向所有元素前添加一个新的元素
    public void addFirst(int e){
        add(0,e);
    }

    //在第index个位置插入一个新元素e
    public void add(int index,int e){

        if(size == data.length)
            throw new IllegalArgumentException("AddLast failed.Array is full.");

        if(index < 0 || index > size)
            throw new IllegalArgumentException("Add failed.Require index >= 0 and index<=size.");

        for(int i = size -1;i >= index ; i--)
            data[i+1] = data[i];

        data[index] = e;

        size ++;
    }

    // 获取index索引位置的元素
    public int get(int index){
        if(index < 0 || index >= size )
            throw new IllegalArgumentException("Get failed.Index is illegal.");
        return data[index];
    }

    //修改index索引位置的元素
    public void set(int index, int e){
        if(index < 0 || index >= size )
            throw new IllegalArgumentException("Set failed.Index is illegal.");
        data[index] = e;
    }

    //查找数组中是否有元素e
    public boolean contains(int e){
        for(int i = 0 ; i < size ; i ++){
            if(data[i]==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
    public int find(int e){
        for(int i = 0 ; i < size ; i ++){
            if(data[i]==e){
                return i;
            }
        }
        return -1;
    }

    //从数组中删除index位置的元素,返回删除的元素
    public int remove(int index){
        if(index < 0 || index >= size )
            throw new IllegalArgumentException("Set failed.Index is illegal.");

        int ret = data[index];
        for(int i = index + 1 ; i < size ; i ++){
            data[i-1] = data[i];
        }
        size --;
        return ret;
    }

    //从数组中删除第一个元素,返回删除的元素
    public int removeFirst(){
        return remove(0);
    }

    //从数组中删除最后一个元素,返回删除的元素
    public int removeLast(){
        return remove(size - 1);
    }

    /**
     * 可能存在多个元素e,稍后自己写findAll和removeAllElement
     * @param e
     */

    //从数组中删除元素e
    public void removeElement(int e){
        int index = find(e);
        if(index != -1)
            remove(index);
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array:size= %d , capacity = %d \n",size,data.length));
        res.append('[');
        for(int i = 0 ;i < size; i ++){
            res.append(data[i]);
            if(i != size -1)
                res.append(",");
        }

        res.append(']');
        return res.toString();
    }
}

main函数

package com.practice;

import com.practice.Array.Array;

public class Main {

    public static void main(String[] args) {
   // write your code here
        Array arr = new Array(20);
        for(int i = 0 ; i < 10 ; i ++)
            arr.addLast(i);
        System.out.println(arr);

        arr.add(1,100);
        System.out.println(arr);

        arr.addFirst(-1);
        System.out.println(arr);

        arr.remove(2);
        System.out.println(arr);

        arr.removeElement(4);
        System.out.println(arr);

        arr.removeFirst();
        System.out.println(arr);
    }
}

 

运行结果

Array:size= 10 , capacity = 20 
[0,1,2,3,4,5,6,7,8,9]
Array:size= 11 , capacity = 20 
[0,100,1,2,3,4,5,6,7,8,9]
Array:size= 12 , capacity = 20 
[-1,0,100,1,2,3,4,5,6,7,8,9]
Array:size= 11 , capacity = 20 
[-1,0,1,2,3,4,5,6,7,8,9]
Array:size= 10 , capacity = 20 
[-1,0,1,2,3,5,6,7,8,9]
Array:size= 9 , capacity = 20 
[0,1,2,3,5,6,7,8,9]