C program to find perfect numbers between 1 to n

Categories C programming 3 mins read

Write a C program to find all Perfect numbers between 1 to n. C program to find all perfect numbers between given range. How to generate all perfect numbers between given interval using loop in C programming. Logic to find all perfect numbers in a given range in C programming.

Example

Input

Input upper limit: 100

Output

Perfect numbers between 1 to 100: 6, 28

Required knowledge

Basic C programming, If statement, For loop, Nested loop

Must know – Program to check divisibility.

What is Perfect number?

Perfect number is a positive integer which is equal to the sum of its proper positive divisors.

For example: 6 is the first perfect number
Proper divisors of 6 are 1, 2, 3
Sum of its proper divisors = 1 + 2 + 3 = 6.
Hence 6 is a perfect number.

Logic to find all Perfect number between 1 to n

Step by step descriptive logic to find Perfect numbers from 1 to n.

  1. Input upper limit from user to find Perfect numbers. Store it in a variable say end.
  2. Run a loop from 1 to end, increment 1 in each iteration. The loop structure should look like for(i=1; i<=end; i++).
  3. For each iteration inside loop print the value of i if it is a Perfect number.

Program to find all perfect numbers between 1 to n

/** * C program to print all Perfect numbers between 1 to n */ #include <stdio.h> int main() { int i, j, end, sum; /* Input upper limit to print perfect number */ printf("Enter upper limit: "); scanf("%d", &end); printf("All Perfect numbers between 1 to %d:\n", end); /* Iterate from 1 to end */ for(i=1; i<=end; i++) { sum = 0; /* Check whether the current number i is Perfect number or not */ for(j=1; j<i; j++) { if(i % j == 0) { sum += j; } } /* If the current number i is Perfect number */ if(sum == i) { printf("%d, ", i); } } return 0; }

Once, you got the logic to print perfect numbers from 1 to n. You can easily modify the logic to print perfect numbers in given range. I am writing the below program with little modification to print perfect numbers in given range.

Program to generate perfect numbers in given range

/** * C program to print all Perfect numbers between 1 to n */ #include <stdio.h> int main() { int i, j, start, end, sum; /* Input lower and upper limit from user */ printf("Enter lower limit: "); scanf("%d", &start); printf("Enter upper limit: "); scanf("%d", &end); printf("All Perfect numbers between %d to %d:\n", start, end); /* Iterate from start to end */ for(i=start; i<=end; i++) { sum = 0; /* Check whether the current number i is Perfect number or not */ for(j=1; j<i; j++) { if(i % j == 0) { sum += j; } } /* If the current number i is Perfect number */ if(sum == i) { printf("%d, ", i); } } return 0; }

Output

Enter lower limit: 1 Enter upper limit: 1000 All Perfect numbers between 1 to 1000: 6, 28, 496,

Happy coding 😉