GATE | GATE-CS-2004 | Question 90

Two matrices M1 and M2 are to be stored in arrays A and B respectively. Each array can be stored either in row-major or column-major order in contiguous memory locations. The time complexity of an algorithm to compute M1 × M2 will be
(A) best if A is in row-major, and B is in column- major order
(B) best if both are in row-major order
(C) best if both are in column-major order
(D) independent of the storage scheme

Answer: (D)
Explanation: This is a trick question. Note that the questions asks about time complexity, not time taken by the program. for time complexity, it doesn’t matter how we store array elements, we always need to access same number of elements of M1 and M2 to multiply the matrices. It is always constant or O(1) time to do element access in arrays, the constants may differ for different schemes, but not the time complexity.
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