If X and Y are two strings of equal length N, then the difference between them is defined as the number of indices i where the i-th character of X and the i-th character of Y are different.

min_differences.rb

def distance(a,b)
  a.split('').zip(b.split('')).select{|a,b| a!=b}.count
end

def min_differences(a,b)
    distances = (0..(b.length - a.length)).map do |index|
      b_sub = b[index...a.length+index]
      distance(a,b_sub)
    end
    distances.min
end

min_differences('chunky', 'nofunky') #=> 2
min_differences('hello', 'xello') #=> 1
min_differences('adaabc', 'aababbc') #=> 2
min_differences('giorgi', 'igroig') #=> 6

For example, the difference between the words "ant" and "art" is 1. You are given two Strings, A and B, where the length of A is less than or equal to the length of B. You can apply an arbitrary number of operations to A, where each operation is one of the following: Choose a character c and add it to the beginning of A. Choose a character c and add it to the end of A. Apply the operations in such a way that A and B have the same length and the difference between them is as small as possible. Return this minimum possible difference. Example 1 input: "chunky", "nofunky" output: 2 You can prepend "n" to "chunky" and you'll get "nchunky". The difference between "nchunky" and "nofunky" is 2. Example 2 input: "hello", "xello" output: 1 Example 3 input: "adaabc", "aababbc" output: 2 Example 4 input: "giorgi", "igroig" output: 6