Google Interview Question for Software Developers
- 6of 6 votes
You are given a matrix with N rows and N columns. Elements in matrix can be either 1 or 0. Each row and column of matrix is sorted in ascending order.
Find number of 0-s in the given matrix.
0 0 1 0 1 1 1 1 1 Answer: 3 0 0 0 0 Answer: 4
Update: Expected complexity is O(log(N)). The best I've seen in comments is still O(N).- emb June 26, 2016 in United States
Update2: Alright, guys, sorry for a bit of trolling. Obviously this is not possible to do faster than O(N). Here is why: take a diagonal (N, 1), (N-1, 2), ... (1, N). Suppose input matrix has all 0's above this diagonal and all 1's under this diagonal. So only diagonal elements vary. Clearly, diagonal elements do not depend on each other. So we have to analyze each diagonal element which is O(N).
Nice job, @gen-y-s :)
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