Here is the link to the problem . I have gone through the editorial but didn't got the approach ( Although I got that we don't need to take more than 2 occurences of a partical triplet [x1,x1+1.x1+2] ) ,I was thinking of DP with three states position i, frequency of i-1th character we took and frequency of i-2nd character we took.
But wasn't able to come up with a solution. Can anybody help me with the solution ?