I was doing this Problem : Count all Longest Common Sub sequences
I completely understand the editorial.
But when i went and look at others people solutions almost every one has used this approach(Not the one given in editorial)(Which too i understand completely):
1].Dynamic Programming Approach to solve “Length of longest common sub sequence”.
2].Dynamic Programming Approach to solve “No of longest common sub sequences”, using step 1.
I am weak at Modular Arithmetic, so i got stuck at this part of above code:
(I think it’s not hard to find this above piece of code).
Why we are adding MOD?
I know that is due to: (dp2[i][j]=(dp2[i-1][j]+dp2[i][j-1]-dp2[i-1][j-1]) can go negative.(I realized this when i looked at other solutions).
But unable to know How adding the MOD will fix the above issue??(Please Someone help).