C PROGRAMMING PROGRAM • LOOPS & NUMBER PROBLEMS

Check Whether a Number Is Perfect

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

BeginnerProper divisorsAccumulatorPerfect number

PROBLEM UNDERSTANDING

Input and expected output

Sample input

Sample output

Perfect number

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

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

    printf("Enter a positive integer: ");
    scanf("%d", &number);
    for (int divisor = 1; divisor <= number / 2; divisor++) {
        if (number % divisor == 0) sum += divisor;
    }
    printf(number > 0 && sum == number ? "Perfect number\n" : "Not a perfect number\n");
    return 0;
}

CURRENT STEP

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SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Perfect number

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Add every proper divisor and compare the sum with the original number.
Display the computed result.

Add every proper divisor and compare the sum with the original number.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

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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.