How to convert N^3 time complexity solution to N^2 time complexity solution in C++ ?

Question

I have written an solution with time complexity of order of N^3 but while submitting this solution i get time limit exceeded error for large input. How can we reduce the time complexity to N^2 as the size of input is 1000 and online judge accepts the solution with time complexity of order of N^2 for this size of input?
Is their any reference or material to learn on how to reduce the time complexity of any solution?
https://code.sololearn.com/c26a226a5A41/?ref=app

Answer 1

MahirShah check out following article,
https://www.geeksforgeeks.org/find-number-of-triangles-possible/

Answer 2

Find the count of triplets that form a triangle in an array

Answer 3

What does your code do?

Answer 4

Thanks