C PROGRAMMING PROGRAM • LOOPS & NUMBER PROBLEMS

Count the Frequency of Every Digit

Learn how to count the frequency of every digit using a clear C program.

IntermediateFrequency arrayDigitsCounting

PROBLEM UNDERSTANDING

Input and expected output

Sample input

Sample output

0 occurs 2 time(s)
1 occurs 1 time(s)
2 occurs 3 time(s)
5 occurs 1 time(s)

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    long long number, value;
    int frequency[10] = {0};

    printf("Enter an integer: ");
    scanf("%lld", &number);
    value = number < 0 ? -number : number;
    do {
        frequency[value % 10]++;
        value /= 10;
    } while (value > 0);
    for (int digit = 0; digit <= 9; digit++) {
        if (frequency[digit] > 0)
            printf("%d occurs %d time(s)\n", digit, frequency[digit]);
    }
    return 0;
}

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EXPECTED OUTPUT FOR THE SAMPLE

0 occurs 2 time(s)
1 occurs 1 time(s)
2 occurs 3 time(s)
5 occurs 1 time(s)

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Use the extracted digit as an index into a fixed ten-element frequency array.
Display the computed result.

Use the extracted digit as an index into a fixed ten-element frequency array.

EFFICIENCY

Time and space complexity

Time complexity

O(d)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

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Initialize variables before using their values.

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Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.