Question 1: You are given n numbers, you need to tell how many ways you can choose 4 numbers out of them so that its sum is T.

Question 2: Coming soon!

Question 3: Coming soon!

Question 4: You are given a binary string, you need to tell the number of ways you can drop some digits so that you can get the string 0011 or 00110011 or 001100110011.

It would be a great help if someone could reply to this discussion with the problem statements of question 2 and 3.