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exactly how i did
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All you need is attention.For C,just dfs from en and output the index when backtracking.I found this after a long thought.
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I got it.The ordinary LCS cannot tell which string is substring and which is subsequence.
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So LCS is one of the wrong algorithms?
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(At first, I wanted to use 01trie to maintain the times a configuration appeared but I think it would get a ME too.
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For D I got the idea, but why if I use an unordered_map to keep track of how many time had a configuration appeared I will get a ME