## Problem Implement a three-way merge: given a **base** version and two branches (`ours` and `theirs`), produce a merged result. If both branches changed the same lines differently, mark as a conflict. Changes to non-overlapping lines are merged automatically. ```python def three_way_merge( base: list[str], ours: list[str], theirs: list[str] ) -> list[str]: # Conflict regions marked as: # [" >>>>>> theirs"] pass ``` ## Example ``` base = ["a", "b", "c", "d"] ours = ["a", "X", "c", "d"] # changed line 2: b->X theirs = ["a", "b", "c", "Y"] # changed line 4: d->Y three_way_merge(base, ours, theirs) # -> ["a", "X", "c", "Y"] (no conflict: different lines changed) ours2 = ["a", "X", "c", "d"] theirs2 = ["a", "Z", "c", "d"] # -> ["a", " >>>>>> theirs", "c", "d"] ``` ## Follow-ups 1. What diff algorithm do you use as the foundation (LCS, Myers diff)? 2. How do you handle moves (a block deleted in one place and inserted elsewhere)? 3. How does this extend to structured formats like JSON or XML where line-level diffs lose semantics?

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Merge Diff: Implement a Three-Way Merge Algorithm for Text Files

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Problem Implement a three-way merge: given a base version and two branches (ours and theirs), produce a merged result. If both branches changed the same lines differently, mark as a conflict. Changes to non-overlapping lines are merged automatically. Example Follow-ups What diff algorithm do you use as the foundation (LCS, Myers diff)? How do you handle moves (a block deleted in one place and inserted elsewhere)? How does this extend to structured formats like JSON or XML where line-level diffs…

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Merge Diff: Implement a Three-Way Merge Algorithm for Text Files

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