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21 days learning challenge 】【 sequential search

2022-08-04 04:16:00 【Alex holding popcorn】

活动地址：CSDN21天学习挑战赛

怕什么真理无穷,进一步有一份的欢喜.

【21天学习挑战赛】顺序查找

我为什么参与挑战赛

1,机缘

读到研一了,暑假器件打开私信发现这个挑战赛就鼓起勇气参加了.

2,期待的收获

A, 本人在华南理工大学攻读专硕,目前研究方向是图像恢复,从事深度学习相关工作,目标是从事Java后端开发.
B, 期待您的反馈,如果有什么不对的地方,欢迎指正！
C, 期待认识志同道合的领域同行或技术交流.
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什么是查找？

在计算机科学中定义为：在一些（有序的/无序的）数据元素中,Find and give by a certain method关键字The process of identical data elements is called lookup.也就是说,We are there for a purpose,Pass in e.g. to the algorithmkey(序号,别名等)或者value(具体的值),returns the data type we want,That is to find.

Definition of sequential lookup

Find a specified element,Traverse the entire data structure（比如表,树,集合等）,to find if the specified element exists.If it exists, the search succeeds,If the specified element is not found at the end of the scan, the search fails.

The pros and cons of sequential search

优势

简单,以一维数组为例,I'm the one from the front to the backforThe loop solves the simple and rude.Sequential sorting is more suitable for unordered data structures with small amounts of data.

劣势

时间复杂度高,以一维数据为例,The time efficiency of sequential search is O（n）,The time efficiency of sequential lookup in a 2D array is O（n^2）

️ 算法实现

public class SequentalSearch {
    
    public static void main(String[] args) {
    
        int[] arr = {
    1, 4, 6, 7, 11};
        int key = 3;
        int value = 11;
        Integer search = Search(arr, null, 11);
        if (search!=null) {
    
            System.out.println("value found: "+search);
        }else {
    
            System.out.println("没找到！");
        }

    }

    /** * @param arr 输入数组 * @param key 如果不为空,返回对应value * @param value 如果不为空,返回对应key */
    public static Integer Search(int[] arr, Integer key, Integer value) {
    
        if (key == null && value == null) {
    
            System.out.println("请输入key或value");
        }
        if (key != null && value != null) {
    
            System.out.println("cannot be entered at the same timekey和value");
        }
        //输入key
        if (key != null) {
    
            for (int i = 0; i < arr.length; i++) {
    
                if (i == key) {
    
                    return arr[i];
                }
            }
        }
        //输入value
        if (value != null) {
    
            for (int i = 0; i < arr.length; i++) {
    
                if (arr[i] == value) {
    
                    return i;
                }
            }
        }
        //没有找到
        return null;
    }
}