TRIANGULAR NUMBERS

• Problem Description

  
  "A triangular number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangular number. The n-th triangular number is the number of dots in a triangle with n dots on a side. . You can learn more about these numbers from Wikipedia (http://en.wikipedia.org/wiki/Triangular_number).
  Your task is to find out if a given integer is a triangular number.
  Input
  The first line contains the single number n (1<n<500) the given integer.
  Output
  If the given integer is a triangular number output YES, otherwise output NO.
  "
  

• CODING ARENA

• #include <stdio.h>

  int triangle(int num)

  {

    if (num<0)

      return 0;

    int n,sum;

    for(n=1;sum<num;n++)

    {

      sum=sum+n;

      if(sum==num)

      return 1;

    }

    return 0;

  }

  int main()

  {

    int n;

    scanf("%d",&n);

    if(triangle(n))

      printf("YES");

    else

      printf("NO");

    return 0;

  }

• Test Case 1

  
  Input (stdin)

  1
  
  

  Expected Output

  YES

• Test Case 2

  
  Input (stdin)

  2
  
  

  Expected Output

  NO