Counting Point Mutations

Problem


Figure 2. The Hamming distance between these two strings is 7. Mismatched symbols are colored red.
Given two strings s and t of equal length, the Hamming distance between s and t, denoted dH(s,t), is the number of corresponding symbols that differ in s and t. See Figure 2.

Given: Two DNA strings s and t of equal length (not exceeding 1 kbp).

Return: The Hamming distance dH(s,t).