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📜  数据结构-线性搜索

📅  最后修改于: 2020-10-15 01:17:12             🧑  作者: Mango

正在搜寻

搜索是在列表中查找某些特定元素的过程。如果列表中存在该元素，则该过程称为成功，并且该过程返回该元素的位置，否则，搜索称为不成功。

有两种流行的搜索方法被广泛使用，以便将某些项目搜索到列表中。但是，算法的选择取决于列表的排列。

  • 线性搜寻
  • 二元搜寻

线性搜寻

线性搜索是最简单的搜索算法，通常称为顺序搜索。在这种类型的搜索中，我们只需完全遍历列表，然后将列表中的每个元素与要查找其位置的项目进行匹配即可。如果找到匹配项，则返回项目的位置，否则算法返回NULL。

线性搜索通常用于搜索未排序项目的无序列表。线性搜索算法如下。

算法

  • LINEAR_SEARCH(A，N，VAL)
  • 步骤1： [INITIALIZE] SET POS = -1
  • 步骤2： [INITIALIZE] SET I = 1
  • 步骤3：在I <= N时重复步骤4
  • 步骤4：如果A [I] = VAL SET POS = I PRINT POS，请转到步骤6 [IF结束] SET I = I + 1 [LOOP LOOP]
  • 第5步：如果POS = -1，则打印“值不代表数组” [IF结束]
  • 步骤6：退出

算法的复杂性

Complexity Best Case Average Case Worst Case
Time O(1) O(n) O(n)
Space O(1)

C程序

#include 
void main ()
{
    int a[10] = {10, 23, 40, 1, 2, 0, 14, 13, 50, 9};
    int item, i,flag;
    printf("\nEnter Item which is to be searched\n");
     scanf("%d",&item);
    for (i = 0; i< 10; i++)
    {
        if(a[i] == item) 
        {
            flag = i+1;
            break;
        } 
        else 
        flag = 0;
    } 
    if(flag != 0)
    {
        printf("\nItem found at location %d\n",flag);
    }
    else
    {
        printf("\nItem not found\n"); 
    }
}

输出：

Enter Item which is to be searched
20
Item not found
Enter Item which is to be searched
23
Item found at location 2

Java程序

import java.util.Scanner;

public class Leniear_Search {
public static void main(String[] args) {
    int[] arr = {10, 23, 15, 8, 4, 3, 25, 30, 34, 2, 19};
    int item,flag=0; 
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter Item ?");
    item = sc.nextInt();
    for(int i = 0; i<10; i++)
    {
        if(arr[i]==item)
        {
            flag = i+1;
            break;
        }
        else 
            flag = 0; 
    }
    if(flag != 0)
    {
        System.out.println("Item found at location" + flag);
    }
    else 
        System.out.println("Item not found");
    
}
}

输出：

Enter Item ?
23
Item found at location 2
Enter Item ?
22
Item not found

C＃程序

using System;
                
public class LinearSearch
{
    public static void Main()
    {
        int item, flag = 0;
        int[]  a= {10, 23, 5, 90, 89, 34, 12, 34, 1, 78}; 
        Console.WriteLine("Enter the item value");
        item = Convert.ToInt32(Console.ReadLine());
        for(int i=0;i<10;i++)
        {
            if(item == a[i])
            {
                flag = i+1;
                break;
            }
            else 
                flag = 0; 
        }
        if(flag != 0 ) 
        {
            Console.WriteLine("Item Found at Location " + flag);
        }
        else 
            Console.WriteLine("Item Not Found");
        
    }
}

输出：

Enter the item value
78
Item Found at Location 10

Enter the item value 
22
Item not found

Python程序

arr = [10,2,3,4,23,5,21,45,90,100];
item = int(input("Enter the item which you want to search "));
for i in range (0,len(arr)):
    if arr[i] == item:
        flag = i+1;
        break;
    else: 
        flag = 0; 
if flag != 0: 
    print("Item found at location %d" % (flag));
else : 
    print("Item not found");

输出：

Enter the item which you want to search 2
Item found at location 2
Enter the item which you want to search 101 
Item not found