Solution to the Longest Common Subsequence needs corrections

The current solution could be spooked with 2 inputs : "ABCDFE" and "FOOBCDBCDE". The logic will create a map that will still end up having the last letter E in sequence.

According to [Wikipedia ](https://en.wikipedia.org/wiki/Longest_common_substring_problem), they are filling in 0 instead of taking the `max (left, above)` for characters that aren't matched.