Sum of Numbers from 1 to n in C

February 24, 2026

C Program to Solve Two Sum Using Brute Force (With Algorithm & Output)

Introduction The Two Sum problem is a popular coding interview question where we must find two indices of an array whose values add up to a given target. This program demonstrates a simple brute-force solution in C using nested loops and dynamic memory allocation. Problem Statement Given an integer array and a target value, return the indices of the two numbers such that they add up to the target. Each input has exactly one solution, and the same element cannot be used twice. The result should return the indices, not the values. If no solution exists, return NULL. Algorithm / Logic Explanation Start the program. Traverse the array using a loop from index 0 to numsSize - 1 . Inside this loop, use another loop starting from i + 1 to numsSize - 1 . For every pair (i, j) , check if nums[i] + nums[j] == target . If condition becomes true: Allocate memory for 2 integers using malloc() . Store indices i and j . Set returnSize = 2 . Return the result poi...

✅ C Program to Calculate Sum from 1 to n

#include <stdio.h>

int main() {
    int n, sum = 0;

    printf("Enter a positive number: ");
    scanf("%d", &n);

    if (n <= 0) {
        printf("Please enter a positive number.\n");
        return 1;
    }

    for (int i = 1; i <= n; i++) {
        sum += i;
    }

    printf("Sum of numbers from 1 to %d is: %d\n", n, sum);

    return 0;
}

📘 Explanation:

✅ This program calculates the sum of all natural numbers from 1 to n.
✅ It uses a for loop to iterate from 1 to the given number n.
✅ On each iteration, it adds the value to a running sum variable.
✅ If the input is non-positive, it displays an error message.

🧾 Sample Output:

Enter a positive number: 5
Sum of numbers from 1 to 5 is: 15

🔑 Keywords:

Sum from 1 to n in C, C loop program, C addition logic, beginner C project, for loop in C, positive number sum

📌 Hashtags:

#CProgramming #ForLoop #BeginnerC #MathInC #SumOfNumbers #InterviewPrep #CodingBasics

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C Program to Solve Two Sum Using Brute Force (With Algorithm & Output)