Count possible triangles Python

PROGRAM TO COUNT THE NUMBER OF POSSIBLE TRIANGLES

def CountTriangles( A):

  

    n = len(A);

  

    A.sort(); 

  

    count = 0;

      

    for i in range(n - 1, 0, -1):

        l = 0;

        r = i - 1;

        while(l < r):

            if(A[l] + A[r] > A[i]):

  

                # If it is possible with a[l], a[r]

                # and a[i] then it is also possible

                # with a[l + 1]..a[r-1], a[r] and a[i]

                count += r - l; 

  

                # checking for more possible solutions

                r -= 1; 

              

            else:

  

                # if not possible check for 

                # higher values of arr[l]

                l += 1; 

    print("No of possible solutions: ", count);

  

# Driver Code

if __name__ == '__main__':

  

    A = [ 4, 3, 5, 7, 6 ]; 

  

    CountTriangles(A);







OUTPUT

No of possible solutions: 9

CREDITS: https://www.geeksforgeeks.org/find-number-of-triangles-possible/