How to check if an Array contains a value or not?

There are many ways for checking whether the array contains any specific value or not, one of them is:

Examples:

Input: arr[] = {10, 30, 15, 17, 39, 13}, key = 17
Output: True

Input: arr[] = {3, 2, 1, 7, 10, 13}, key = 20
Output: False

Approach:

Using in-built functions: In C language there is no in-built function for searching

C++

#include <bits/stdc++.h>
using namespace std;

int main()
{
    vector<int> v{ 10, 25, 15, 12, 14 };
    int key = 15;

    // Using inbuilt function 'find'
    if (find(v.begin(), v.end(), key) != v.end())
        cout << key << " is present in the array";
    else
        cout << key << " is not present in the array";
    return 0;
}

Java

/*package whatever // do not write package name here */

import java.io.*;
import java.util.Arrays;

class GFG {
    public static void main(String[] args)
    {
        Integer arr[] = { 10, 25, 15, 12, 14 };
        int key = 15;

        // Using inbuilt function 'contains'
        boolean found = Arrays.asList(arr).contains(key);
        if (found == true) {
            System.out.println(
                key + " is present in the array");
        }
        else {
            System.out.println(
                key + " is not present in the array");
        }
    }
}

Python3

if __name__ == '__main__':
    arr = [10, 25, 15, 12, 14]
    key = 15
    found = False

    if key in arr:
        found = True

    if found == True:
        print(key, end = " is present in the array")
    else:
        print(key, end = " is not present in the array")

C#

// C# Code for above approach
using System;

public class GFG {
    public static void Main(string[] args)
    {
        int []arr = { 10, 25, 15, 12, 14 };
        int key = 15;

        // Using inbuilt function 'contains'
        bool found = Array.Exists(arr, x => x == key);
        if (found == true) {
            Console.WriteLine(key + " is present in the array");
        }
        else {
            Console.WriteLine(key + " is not present in the array");
        }
    }
}

// This code is contributed by AnkThon

PHP

<?php
    $arr = array(10, 25, 15, 12, 14);
    $key = 15;
     if (in_array("$key", $arr)){
        echo "$key is present in the array";
     }
     else{
        echo "$key is not present in the array";
     }
?>

Javascript

<script>
      const arr = [10, 25, 15, 12, 14];
      const key = 15
      if(arr.includes(key) == true){
        console.log( key + " is present in the array");
      }
      else{
        console.log( key + " is not present in the array");
      }
</script>

Output

15 is present in the array

Time Complexity: O(N)

Auxiliary Space: O(1)

Apart from these inbuilt functions, there are other methods that one can use like:

• Linear search
• Binary search
• Ternary search, and
• Other searching algorithms