无序数组增删改查

傷城~ 2024-03-26 18:55 57阅读 0赞

### 无序数组 ###

#### **增：** ####

public class ArrNoSortDemo {
        private int[]arr = new int[20];
        private int flag = 0;
        
        //不考虑数组容量的增，不严谨
        public void  add(int x){
            arr[flag] = x;
            flag++;
        }
        
        
        public void  adds(int x){
        if(flag==arr.length){
            int[] arrNew=new int[arr.length*2];
            for (int i = 0;i<flag;i++){
                arrNew[i]=arr[i];
            }
            arr=arrNew;
        }
        arr[flag]=x;
        flag++;
    }
    }

![a7ac9e4a3aea424db4de33acae4c043d.png][]

#### 查： ####

//查
    public int getIndex(int x){
        for (int i = 0;i<flag;i++){
            if (x==arr[i]){
                return i;
            }
        }
        return -1;
    }

![2591b8781fa8462dbae813c120001498.png][]

#### 改： ####

//改
    public void change(int oldNum,int newNum){
        int index = getIndex(oldNum);
        arr[index]=newNum;
    }

![cda60072430247748c9b6f4523a3e77a.png][]

#### 删除： ####

方法一：（不考虑重复的情况：）

![8d3c30996a964374888a190c9cb50cec.png][]

方法二：

![d64126ffea6343618c449d817fc91b0c.png][]

![03e2d5fdfe434e2fb5d726c5a66f8630.png][]

### 二分查找： ###

查找x，L指针指向数组开头，R指针指向数组末尾，C指针指向（L+R）/ 2

第一次遍历，如果x>c箭头所指的数，则保留C箭头右边的数据，L箭头指向C箭头的位置（x < c箭头所指的数，则保留C箭头左边的数据，R箭头指向C箭头的位置），C箭头指向此时L箭头和R箭头之和的一半，在和x对比，以此类推直到找到x![3fb78f29e4a74c48b58d238d309de6e2.png][]

public static void main(String[] args) {
         int[] arr = {1,2,3,4,5,6,7,8,11,22};
          getIndex(arr,4);
    }
    public static void getIndex(int[]arr,int x){
         int left = 0;
         int right= arr.length - 1;
         while (left <= right){
              int middle = (left+right)/2;
              if(arr[middle] == x){
                   System.out.println("索引的位置是:"+middle);
                   return;
              }else if(arr[middle]< x){
                   left = middle +1;
              }else {
                   right = middle - 1;
              }
         }
         System.out.println("查询失败");
    }

画图演示：![85db6aa8defe4244b6aceb4b153e69a8.png][]

![6d13434b754e4ac4962c553441199159.png][]

--------------------

以上是我学习了《数据结构》的无序数组的demo练习，从简单的做起，循序渐进！加油![7efd2a0e7b9f4021ae1a72925cd959ee.png][]

[a7ac9e4a3aea424db4de33acae4c043d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/61e9fc4b1055450fad8cfe161c9a5db8.png
[2591b8781fa8462dbae813c120001498.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/3985f744187c476399504104d559323c.png
[cda60072430247748c9b6f4523a3e77a.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/ceb8b49056474c49b64a1e82f4c8492f.png
[8d3c30996a964374888a190c9cb50cec.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/a06b2e012efb4aa3ae65bd00bac4d61d.png
[d64126ffea6343618c449d817fc91b0c.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/5d438a6f87aa4caca9b48ba809c949c3.png
[03e2d5fdfe434e2fb5d726c5a66f8630.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/3bd137077ce44601801be1743a55f344.png
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[85db6aa8defe4244b6aceb4b153e69a8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/d1f314c078d94275bcb7738e6ae4e4bd.png
[6d13434b754e4ac4962c553441199159.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/d3e0c7efbe2943d7900f7d1f735334d0.png
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