Search a 2D Matrix
Given a 2D matrix where: - Each row is sorted in ascending order - First element of each row > last element of previous row Return true if target exists in matrix, false otherwise Must use O(log(m*n)) time complexity Example: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3 => true
Binary search is the tool here, but the real test is whether your invariant stays crisp. Interviewers love it because it reveals your boundary precision and your edge-case discipline. Interviewers care more about airtight boundaries than speed here.
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