Efficient ways to compare a variable with multiple values

In this article, we will discuss the ways to compare a variable with values.

Method 1: The idea is to compare each variable individually to all the multiple values at a time.

Program 1:

C++

// C++ program to compare one variable
// with multiple variable
#include <iostream>
using namespace std;

// Driver Code
int main()
{
    // Variable to be compared
    char character = 'a';

    // Compare the given variable
    // with vowel using || operator

    // Check for vowel
    if  (character == ('a' || 'e'
            || 'i' || 'o'
                    || 'u')) {
        cout << "Vowel";
    }

    // Otherwise Consonant
    else {
        cout << "Consonant";
    }

    return 0;
}

Java

// Java program to compare one variable
// with multiple variable
import java.util.*;

class GFG
{

// Driver Code
public static void main(String[] args)
{
    // Variable to be compared
    char character = 'a';

    // Compare the given variable
    // with vowel using || operator
    // Check for vowel
    if (character == ('a' || 'e'
            || 'i' || 'o'
                    || 'u')) {
        System.out.print("Vowel");
    }

    // Otherwise Consonant
    else {
        System.out.print("Consonant");
    }

}
}

// This code is contributed by Rajput-Ji

Python3

# Python program to compare one variable
# with multiple variable

# Driver Code
if __name__ == '__main__':

    # Variable to be compared
    character = 'a';

    # Compare the given variable
    # with vowel using or operator
    # Check for vowel
    if (character == ('a' or 'e' or 'i' or 'o' or 'u')):
        print("Vowel");

    # Otherwise Consonant
    else:
        print("Consonant");

# This code contributed by shikhasingrajput

C#

// C# program to compare one variable
// with multiple variable
using System;

class GFG
{

// Driver Code
public static void Main(String[] args)
{
    // Variable to be compared
    char character = 'a';

    // Compare the given variable
    // with vowel using || operator
    // Check for vowel
    if (character == ('a' || 'e'
            || 'i' || 'o'
                    || 'u')) {
        Console.Write("Vowel");
    }

    // Otherwise Consonant
    else {
        Console.Write("Consonant");
    }
}
}

// This code is contributed by 29AjayKumar

Javascript

<script>

// Javascript program to compare one variable
// with multiple variable

// Variable to be compared
var character = 'a';

// Compare the given variable
// with vowel using || operator

// Check for vowel
if  (character == ('a'. charCodeAt(0) ||
                   'e'. charCodeAt(0) ||
                   'i'. charCodeAt(0) ||
                   'o'. charCodeAt(0) ||
                   'u'. charCodeAt(0)))
{
    document.write("Vowel");
}

// Otherwise Consonant
else
{
    document.write("Consonant");
}

// This code is contributed by SoumikMondal

</script>

Output

Consonant

Time Complexity: O(1) because constant operations are being performed
Auxiliary Space: O(1)

Explanation:
The above code gives the Wrong Answer or error as comparing variable in the above way is incorrect and it forced to code in the below way:

C++

// C++ program to compare one variable
// with multiple variable
#include <iostream>
using namespace std;

// Driver Code
int main()
{
    // Variable to be compared
    char character = 'a';

    // Compare the given variable
    // with vowel individually

    // Check for vowel
    if (character == 'a'
        || character == 'e'
        || character == 'i'
        || character == 'o'
        || character == 'u') {
        cout << "Vowel";
    }

    // Otherwise Consonant
    else {
        cout << "Consonant";
    }

    return 0;
}

Java

// Java program to compare
// one variable with multiple
// variable
import java.util.*;
class GFG{

// Driver Code
public static void main(String[] args)
{
  // Variable to be compared
  char character = 'a';

  // Compare the given variable
  // with vowel using || operator

  // Check for vowel
  if (character == 'a' || character == 'e' ||
      character == 'i' || character == 'o' ||
      character == 'u')
  {
    System.out.print("Vowel");
  }

  // Otherwise Consonant
  else
  {
    System.out.print("Consonant");
  }
}
}

// This code is contributed by 29AjayKumar

Python3

# Python3 program to compare
# one variable with multiple
# variable

# Driver Code
if __name__ == '__main__':

    # Variable to be compared
    character = 'a';

    # Compare the given variable
    # with vowel using or operator

    # Check for vowel
    if (character == 'a' or
        character == 'e' or
        character == 'i' or
        character == 'o' or
        character == 'u'):
        print("Vowel");

    # Otherwise Consonant
    else:
        print("Consonant");

# This code contributed by Princi Singh

C#

// C# program to compare
// one variable with multiple
// variable
using System;
class GFG{

// Driver Code
public static void Main(String[] args)
{
  // Variable to be compared
  char character = 'a';

  // Compare the given variable
  // with vowel using || operator

  // Check for vowel
  if (character == 'a' || character == 'e' ||
      character == 'i' || character == 'o' ||
      character == 'u')
  {
    Console.Write("Vowel");
  }

  // Otherwise Consonant
  else
  {
    Console.Write("Consonant");
  }
}
}

// This code is contributed by gauravrajput1

Javascript

<script>

// javascript program to compare one variable
// with multiple variable


// Driver Code

function checkCharacter(character)
{

    // Compare the given variable
    // with vowel using || operator
    // Check for vowel

if (character == 'a' || character == 'e' ||
      character == 'i' || character == 'o' ||
      character == 'u')   {
      document.write("Vowel");
    }

    // Otherwise Consonant
    else {
        document.write("Consonant");
    }
}

// Driver Code

checkCharacter('a');

// This code is contributed by bunnyram19.
</script>

Output

Vowel

Time Complexity: O(1) because constant operations are being performed
Auxiliary Space: O(1)

Method 2 – using Bitmasking: Another approach is to check among multiple groups of values and then create a bitmask of the values and then check for that bit to be set.

Program 2:

C++

// C++ program to compare a value
// with multiple values
#include <iostream>
using namespace std;

// Driver Code
int main()
{
    // Create bitmasks
    unsigned group_1 = (1 << 1) | (1 << 2) | (1 << 3);
    unsigned group_2 = (1 << 4) | (1 << 5) | (1 << 6);
    unsigned group_3 = (1 << 7) | (1 << 8) | (1 << 9);

    // Values to be checked
    int value_to_check = 9;

    // Checking with created bitmask
    if ((1 << value_to_check)
        & group_1) {
        cout << "found a match in group 1";
    }
    if ((1 << value_to_check)
        & group_2) {
        cout << "found a match in group 2";
    }
    if ((1 << value_to_check)
        & group_3) {
        cout << "found a match in group 3";
    }

    return 0;
}

Java

// Java program to compare a value
// with multiple values
import java.util.*;
class GFG{

// Driver Code
public static void main(String[] args)
{
    // Create bitmasks
    int group_1 = (1 << 1) |
                  (1 << 2) | (1 << 3);
    int group_2 = (1 << 4) |
                  (1 << 5) | (1 << 6);
    int group_3 = (1 << 7) |
                  (1 << 8) | (1 << 9);

    // Values to be checked
    int value_to_check = 9;

    // Checking with created bitmask
    if (((1 << value_to_check) &
          group_1) > 0)
    {
        System.out.print("found a match " +
                         "in group 1");
    }
    if (((1 << value_to_check) &
          group_2) > 0)
    {
        System.out.print("found a match " +
                         "in group 2");
    }
    if (((1 << value_to_check) &
          group_3) > 0)
    {
        System.out.print("found a match " +
                         "in group 3");
    }
}
}

// This code is contributed by shikhasingrajput

Python3

# Python3 program to compare a value
# with multiple values

# Driver Code
if __name__ == '__main__':

    # Create bitmasks
    group_1 = (1 << 1) | (1 << 2) | (1 << 3)
    group_2 = (1 << 4) | (1 << 5) | (1 << 6)
    group_3 = (1 << 7) | (1 << 8) | (1 << 9)

    # Values to be checked
    value_to_check = 9

    # Checking with created bitmask
    if (((1 << value_to_check) & group_1) > 0):
        print("found a match " + "in group 1")

    if (((1 << value_to_check) & group_2) > 0):
        print("found a match " + "in group 2")

    if (((1 << value_to_check) & group_3) > 0):
        print("found a match " + "in group 3")

# This code is contributed by gauravrajput1

C#

// C# program to compare a value
// with multiple values
using System;
class GFG{

// Driver Code
public static void Main(String[] args)
{
  // Create bitmasks
  int group_1 = (1 << 1) |
                (1 << 2) |
                (1 << 3);
  int group_2 = (1 << 4) |
                (1 << 5) |
                (1 << 6);
  int group_3 = (1 << 7) |
                (1 << 8) |
                (1 << 9);

  // Values to be checked
  int value_to_check = 9;

  // Checking with created
  // bitmask
  if (((1 << value_to_check) &
        group_1) > 0)
  {
    Console.Write("found a match " +
                  "in group 1");
  }
  if (((1 << value_to_check) &
        group_2) > 0)
  {
    Console.Write("found a match " +
                  "in group 2");
  }
  if (((1 << value_to_check) &
        group_3) > 0)
  {
    Console.Write("found a match " +
                  "in group 3");
  }
}
}

// This code is contributed by gauravrajput1

Javascript

<script>

// JavaScript program to compare a value
// with multiple values

// Create bitmasks
    let group_1 = (1 << 1) |
                  (1 << 2) | (1 << 3);
    let group_2 = (1 << 4) |
                  (1 << 5) | (1 << 6);
    let group_3 = (1 << 7) |
                  (1 << 8) | (1 << 9);

    // Values to be checked
    let value_to_check = 9;

    // Checking with created bitmask
    if (((1 << value_to_check) &
          group_1) > 0)
    {
        document.write("found a match " +
                         "in group 1");
    }
    if (((1 << value_to_check) &
          group_2) > 0)
    {
        document.write("found a match " +
                         "in group 2");
    }
    if (((1 << value_to_check) &
          group_3) > 0)
    {
        document.write("found a match " +
                         "in group 3");
    }


// This code is contributed by unknown2108

</script>

Output

found a match in group 3

Time Complexity: O(1) because constant operations are being performed
Auxiliary Space: O(1)

Note: This approach works best for values that don’t exceed the natural size of your CPU. It would typically be 64 in modern times. The general solution to this problem using Template from C++11. Below is the program for the same:

Program 3:

C++

// C++ program for comparing variable
// with multiples variable
#include <algorithm>
#include <initializer_list>
#include <iostream>
using namespace std;

template <typename T>

// Function that checks given variable
// v in the list lst[]
bool is_in(const T& v,
           std::initializer_list<T> lst)
{
    return (std::find(std::begin(lst),
                      std::end(lst), v)
            != std::end(lst));
}

// Driver Code
int main()
{
    // Number to be compared
    int num = 10;

    // Compare with multiple variables
    if (is_in(num, { 1, 2, 3 }))
        cout << "Found in group" << endl;
    else
        cout << "Not in group" << endl;

    // Character to be compared
    char c = 'a';

    // Compare with multiple variables
    if (is_in(c, { 'x', 'a', 'c' }))
        cout << "Found in group" << endl;
    else
        cout << "Not in group" << endl;

    return 0;
}

Python3

# Python program for above approach
import math

# Function that checks given variable
# v in the list lst[]
def is_in(v, lst):
    return v in lst


# Driver Code

# Number to be compared
num = 10

# Compare with multiple variables
if (is_in(num, [1, 2, 3] )):
    print("Found in group")
else:
    print("Not in group")

# Character to be compared
c = 'a'

# Compare with multiple variables
if (is_in(c,  ['x', 'a', 'c'] )):
    print("Found in group")
else:
    print("Not in group")

#This code is contributed by shubhamsingh10

C#

// C# program for the above approach
using System;
using System.Linq;

public static class Extensions
{

    // Function that checks given variable
    // v in the list lst[]
    public static bool is_in<T>(this T[] array,
                                T target)
    {
        return array.Contains(target);
    }
}

class GFG{

// Driver Code
static public void Main ()
{

    // Number to be compared
    int num = 10;
    int [] arr = { 1, 2, 3 };

    // Compare with multiple variables
    if (arr.is_in(num))
        Console.WriteLine("Found in group");
    else
        Console.WriteLine("Not in group");

    // Character to be compared
    char c = 'a';
    char[] arr1 = { 'x', 'a', 'c' };

    // Compare with multiple variables
    if (arr1.is_in(c))
        Console.WriteLine("Found in group");
    else
        Console.WriteLine("Not in group");
}
}

// This code is contributed by shubhamsingh10

Javascript

// Javascript code addition

// Function that checks given variable
// v in the array arr[]
function isIn(v, arr) {
    return arr.includes(v);
}

// Driver Code

// Number to be compared
let num = 10;

// Compare with multiple variables
if (isIn(num, [1, 2, 3])) {
    console.log("Found in group");
} else {
    console.log("Not in group");
}

// Character to be compared
let c = 'a';

// Compare with multiple variables
if (isIn(c, ['x', 'a', 'c'])) {
    console.log("Found in group");
} else {
    console.log("Not in group");
}

// The code is contributed by Arushi Goel.

Java

import java.util.Arrays;
import java.util.List;

public class Main {
    // Function that checks given variable
    // v in the list lst
    static <T> boolean is_in(T v, List<T> lst)
    {
        return lst.contains(v);
    }

    // Driver Code
    public static void main(String[] args)
    {
        // Number to be compared
        int num = 10;

        // Compare with multiple variables
        if (is_in(num, Arrays.asList(1, 2, 3)))
            System.out.println("Found in group");
        else
            System.out.println("Not in group");

        // Character to be compared
        char c = 'a';

        // Compare with multiple variables
        if (is_in(c, Arrays.asList('x', 'a', 'c')))
            System.out.println("Found in group");
        else
            System.out.println("Not in group");
    }
}

Output

Not in group
Found in group

Time Complexity: O(1) because constant operations are being performed
Auxiliary Space: O(1)

Note: It is not very efficient though when not used with primitive types. For std::string it will produce an error. This task became really easy with C++17, as it comes with Fold Expression. This is generally called Folding which helps to express the same idea with less code and it works well with any data type. Here, “||” operator to reduce all the Boolean results to a single one which is only False if all the comparison results False. Below is the program for the same:

Program 4:

C++

// C++ program for comparing variable
// with multiple variables
#include <algorithm>
#include <initializer_list>
#include <iostream>
#include <string>
using namespace std;

template <typename First, typename... T>

// Function that checks given variable
// first in the list t[]
bool is_in(First&& first, T&&... t)
{
    return ((first == t) || ...);
}

// Driver Code
int main()
{
    // Number to be compared
    int num = 10;

    // Compare using template
    if (is_in(num, 1, 2, 3))
        cout << "Found in group" << endl;
    else
        cout << "Not in group" << endl;

    // String to be compared
    string c = "abc";

    // Compare using template
    if (is_in(c, "xyz", "bhy", "abc"))
        cout << "Found in group" << endl;
    else
        cout << "Not in group" << endl;

    return 0;
}

Javascript

// Function that checks if the given variable is in the list
function is_in(first, ...t) {
    return t.includes(first);
}

// Driver Code
// Number to be compared
let num = 10;

// Compare using template
if (is_in(num, 1, 2, 3))
    console.log("Found in group");
else
    console.log("Not in group");

// String to be compared
let c = "abc";

// Compare using template
if (is_in(c, "xyz", "bhy", "abc"))
    console.log("Found in group");
else
    console.log("Not in group");

Output:

Time Complexity: O(1) because constant operations are being performed
Auxiliary Space: O(1)