DNA Mutations
Easy · rating 1000 · strings
Two DNA strands of equal length are compared. Read two lines, strands a and b. Print the number of positions at which the nucleotides differ (the Hamming distance).
Editorial
DNA Mutations counts the positions at which two equal-length strands differ — the Hamming distance, used throughout genetics and error-correcting codes.
Approach
Walk both strings in lockstep and count mismatches. Because the lengths are equal, a single pass suffices.
return sum(1 for x, y in zip(a, b) if x != y)Complexity
Time: O(n). Space: O(1).