Give me proof why following approach is wrong

My approach wrong approach is such.

Read cur number X.

Find CNT count of numbers Y (Y>X) already read.

Find number of ways to pick K-1 items from set of CNT distinctive items.

Add that number to ANSWER. Find modulo.

*Edited by author 11.05.2017 13:28*

Re: Give me proof why following approach is wrong

Posted by

sak3t 22 Jun 2017 13:53

Your solution is wrong. See for example

6 3

3 4 5 6 2 1

when you read 2, all the numbers before it are > 2 and hence you'll add to your sum, all the possible pairs in previous 4 numbers. But 3 4 5 6 can't make any pair such that a_i > a_{i+1}. Hence your solution doesn't work.

*Edited by author 22.06.2017 13:55*