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Longest Common Subsequence
Classic dynamic programming: the longest sequence of letters both strings share, in order.
🔴 ExtremeDifficulty
The challenge
Given "ABCBDAB" and "BDCABA", find the length of their longest common subsequence -- the longest sequence of characters that appears in both strings in the same relative order (not necessarily contiguous) -- and print the length.
🧠 Need a hint? (Python)
Build a 2D table dp where dp[i][j] is the LCS length of a[:i] and b[:j]. If a[i-1] == b[j-1], dp[i][j] = dp[i-1][j-1] + 1; otherwise dp[i][j] = max(dp[i-1][j], dp[i][j-1]).
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