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C Code: https://ideone.com/E4cLHi
Python code: https://ideone.com/qi1QBh
C++ Code: https://ideone.com/sDHVPs
At 23:45, in the video yellow boxes are not overlapping sub problems because if there was a match in the last character the other part of the tree will never be evaluated.So yellow boxes does not form overlapping sub problems. At 25:20 The worst case time complexity of LCS solution will be O(2^(m+n)). The worst case happens when there is no common sub sequence present in X and Y ( that is LCS is 0) and each recursive call will end up in two recursive calls.