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C# Program to Find the Frequency of a Digit in a Number

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C# programs to find the frequency of a digit in a number have been shown here. Frequency denotes the number of occurrences of an element. For example, if a number is 202223, the frequency of the digit 2 in that number is 4.

In the following section, the algorithm, pseudocode, and time complexity of the programs have also been covered.






1. Algorithm to find the frequency of a digit in a number


1. Take a number n and a digit d as inputs.

2. Initialize a counter c = 0.

3. If n = d = 0, set c = 1 and go to step 7.

4. Perform c = c + 1, if n mod 10 = d

5. Perform n = floor(n / 10)

6. Go to step 4, if n > 0, else go to step 7

7. Declare value of c as the output.




2. Pseudocode to find the frequency of a digit in a number


Input : A number $n$ and a digit $d$

Output : Frequency of $d$ in $n$

1. Procedure countFrequency($n$, $d$):

2. $c \leftarrow 0$

3. If $n = 0$ and $d = 0$:

4. $c \leftarrow 1$

5. Else:

6. Repeat until $n = 0$

7. If $n \mod 10 = d$:

8. $c \leftarrow c + 1$

9. $n \leftarrow \lfloor{\frac{n}{10}}\rfloor$

10. Return $c$

11. End Procedure





3. Time complexity to find the frequency of a digit in a number


Time Complexity: O(log(n))

Where n is the input number.





4. Program & Output to find the frequency of a digit in a number




4.1. C# Program & Output to find the frequency of a digit in a number Using Iteration

Code has been copied
/*****************************
       alphabetacoder.com
 C# program to count frequency 
 of a digit in a number
******************************/

using System;

namespace DigitFrequency {
    class Program {
        static void Main(string[] args) {
            // declare variables
            int num, d, r, t, count = 0;

            // take input
            Console.Write("Enter the integer = ");
            num = Convert.ToInt32(Console.ReadLine());
            Console.Write("Enter the digit = ");
            d = Convert.ToInt32(Console.ReadLine());

            // copy
            t = num;

            //count the frequency of the digit
            if (num == 0 && d == 0) {
                count++;
            }
            while (num > 0) {
                // find unit digit of current number
                r = num % 10;
                // Increase the counter if unit digit = target digit
                if (r == d)
                    count++;

                num = num / 10;
            }

            // display result
            Console.WriteLine("Frequency of " + d + " in " + t + " = " + count);

            // wait for user to press any key
            Console.ReadKey();
        }
    }
}

Output

Enter the integer = 7705787

Enter the digit = 7

Frequency of 7 in 7705787 = 4





4.2. C# Program & output to find the frequency of a digit in a number using recursion

Code has been copied
/***********************************
        alphabetacoder.com
 C# program to count frequency of a 
 digit in a number using recursion
************************************/

using System;

namespace DigitFrequency {
    class Program {
        // recursive function to count frequency
        // of a digit in an integer
        static int count_frequency(int num, int d) {
            // exit condition
            if (num == 0)
                return 0;
            // call the function
            return ((num % 10 == d ? 1 : 0) + count_frequency(num / 10, d));
        }

        static void Main(string[] args) {
            // declare variables
            int num, d, count = 0;

            // take input
            Console.Write("Enter the integer = ");
            num = Convert.ToInt32(Console.ReadLine());
            Console.Write("Enter the digit = ");
            d = Convert.ToInt32(Console.ReadLine());

            // if both inputs are zero
            if (num == 0 && d == 0)
                count = 1;
            else {
                //count the frequency of the digit in a 
                //number by calling recursive function
                count = count_frequency(num, d);
            }

            // display result
            Console.WriteLine("Frequency of " + d + " in " + num + " = " + count);

            // wait for user to press any key
            Console.ReadKey();
        }
    }
}

Output

Enter the integer = 6855663

Enter the digit = 6

Frequency of 6 in 6855663 = 3





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