C PROGRAMMING PROGRAM • LOOPS & NUMBER PROBLEMS

Check Whether a Number Is an Armstrong Number

Learn how to check whether a number is an armstrong number using a clear C program.

IntermediateDigit countPowerArmstrong number

PROBLEM UNDERSTANDING

Input and expected output

Sample input

Sample output

Armstrong number

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int number, value, digits = 0, sum = 0;

    printf("Enter a non-negative integer: ");
    scanf("%d", &number);
    if (number < 0) {
        printf("Use a non-negative integer.\n");
        return 0;
    }
    value = number;
    do {
        digits++;
        value /= 10;
    } while (value > 0);
    value = number;
    do {
        int digit = value % 10;
        int power = 1;
        for (int count = 0; count < digits; count++) power *= digit;
        sum += power;
        value /= 10;
    } while (value > 0);
    printf(sum == number ? "Armstrong number\n" : "Not an Armstrong number\n");
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Armstrong number

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Count the digits, raise each digit to that count, add the powers and compare with the original.
Display the computed result.

Count the digits, raise each digit to that count, add the powers and compare with the original.

EFFICIENCY

Time and space complexity

Time complexity

O(d²)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

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.