What is the time complexity of longest common subsequence?

Worst case O(m × n). Space complexity is O(m × n). Replaces checking all 2^m subsequences with (m+1)(n+1) cells.

Longest common subsequence

medium

The table gives the length; the traceback gives the subsequence. This is the algorithm behind `diff`, DNA alignment and plagiarism detection.

Worst O(m × n)Space O(m × n)

Loading the longest common subsequence engine…

Three neighbours, three edits, one minimum.

The O(n²) table, and the O(n log n) trick that replaces it.

Longest palindromic substring in O(n).