C PROGRAMMING PROGRAM • LOOPS & NUMBER PROBLEMS

Find the Sum of the First N Natural Numbers

Learn how to find the sum of the first n natural numbers using a clear C program.

BeginnerLoop accumulationNatural numberslong long

PROBLEM UNDERSTANDING

Input and expected output

Sample input

Sample output

Sum = 55

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int limit;
    long long sum = 0;

    printf("Enter N: ");
    scanf("%d", &limit);
    for (int number = 1; number <= limit; number++)
        sum += number;
    printf("Sum = %lld\n", sum);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Sum = 55

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Accumulate each integer from 1 to N in a long long sum.
Display the computed result.

Accumulate each integer from 1 to N in a long long sum.

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.