C Program to Check Triangular Number

Posted in C Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 61 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, various mathematical properties of numbers often pique our interest. One such property is whether a number is a triangular number.

A triangular number or triangle number is the sum of the natural numbers up to a certain value.

In this tutorial, we'll explore a C program to check if a given number is a triangular number.

📄 Example

Let's delve into the C code that checks whether a given number is a triangular number.

isTriangularNumber.c

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#include <stdio.h>
#include <math.h>

// Function to check if a number is a triangular number
int isTriangularNumber(int num) {
  // Formula to check triangular number
  int n = (int) sqrt(2 * num);
  return (n * (n + 1)) / 2 == num;
}

// Driver program
int main() {
  // Replace this value with your desired number
  int number = 10;

  // Check if the number is a triangular number
  if (isTriangularNumber(number)) {
    printf("%d is a triangular number.\n", number);
  } else {
    printf("%d is not a triangular number.\n", number);
  }

  return 0;
}

💻 Testing the Program

To test the program with different numbers, simply replace the value of number in the main function.

Output

10 is a triangular number.

Compile and run the program to check if the given number is a triangular number.

🧠 How the Program Works

The program defines a function isTriangularNumber that checks if a given number is a triangular number.
Inside the main function, replace the value of number with the desired number to check.
The program then calls the isTriangularNumber function and prints whether the number is a triangular number or not.

📏 Between the Given Range

Let's take a look at the C code that checks and displays triangular numbers in the range of 1 to 50.

isTriangular.c

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#include <stdio.h>

// Function to check if a number is triangular
int isTriangular(int num) {
  int sum = 0, n = 1;

  while (sum < num) {
    sum += n;
    ++n;
  }

  return (sum == num);
}

// Driver program
int main() {
  printf("Triangular Numbers in the Range 1 to 50:\n");

  for (int i = 1; i <= 50; ++i) {
    if (isTriangular(i)) {
      printf("%d ", i);
    }
  }

  return 0;
}

💻 Testing the Program

Output

Triangular Numbers in the Range 1 to 50:
1 3 6 10 15 21 28 36 45

Compile and run the program to see the triangular numbers in the range of 1 to 50.

🧠 How the Program Works

The program defines a function isTriangular that checks if a given number is triangular.
Inside the function, it uses a while loop to find the triangular number by iteratively adding natural numbers.
The main function iterates through the numbers from 1 to 50 and prints those that are triangular.

🧐 Understanding the Concept of Triangular Numbers

Before delving into the code, let's take a moment to understand the concept of triangular numbers.

A triangular number is the sum of the natural numbers up to a certain value, and it can be represented by the formula T_n = n * (n + 1) / 2, where n is a non-negative integer.

For example, T₃ = 1 + 2 + 3 = 6 is a triangular number.