Topological sorting closed

Question

My ques. is not the no. of topological sort as i have computed it myself. My problem is can someone please telll me a efficient approach as tree method is taking a lot of time here, like by use of combinatorics, can we find it easily, i.e in less time. and if possible, pls provide general approach apart from tree method.

Comments

https://gateoverflow.in/109278/made-easy-cbt-2017-q22

---

@dulqar, bhai problem is not the no. of topological sort, it is that is there any efficient way using combinatorics? i solved it and it took around 4 min. for me to get the answer. i don't want it to happen in exam.

But thanks for your quick reply i appreciate. :)

---

Read the comments and all. It is answered with combination . brute force even Debashih Deka has saaid an general approach . What I meant is . Instead of opening a new thread if you ask it over there will defenitely get a much quick reply

---

Hi, had similar difficulty what you are facing. please refer this video https://www.youtube.com/watch?v=a3UDL-v6-44.

Hope it will be helpful :-)