Python3 Program to Minimize characters to be changed to make the left and right rotation of a string same

# Python3 Program of the
# above approach

# Function to find the minimum
# characters to be removed from
# the string
def getMinimumRemoval(str):
  
    n = len(str)

    # Initialize answer by N
    ans = n

    # If length is even
    if(n % 2 == 0):

        # Frequency array for odd
        # and even indices
        freqEven = {}
        freqOdd = {}
        for ch in range(ord('a'), 
                        ord('z') + 1):
            freqEven[chr(ch)] = 0
            freqOdd[chr(ch)] = 0

        # Store the frequency of the
        # characters at even and odd
        # indices
        for i in range(n):
            if(i % 2 == 0):
                if str[i] in freqEven:
                    freqEven[str[i]] += 1
            else:
                if str[i] in freqOdd:
                    freqOdd[str[i]] += 1

        # Stores the most occurring 
        # frequency for even and 
        # odd indices
        evenMax = 0
        oddMax = 0

        for ch in range(ord('a'), 
                        ord('z') + 1):
            evenMax = max(evenMax, 
                      freqEven[chr(ch)])
            oddMax = max(oddMax, 
                     freqOdd[chr(ch)])

        # Update the answer
        ans = ans - evenMax - oddMax

    # If length is odd
    else:

        # Stores the frequency of the
        # characters of the string
        freq = {}
        
        for ch in range('a','z'):
            freq[chr(ch)] = 0
        for i in range(n):
            if str[i] in freq:
                freq[str[i]] += 1

        # Stores the most occurring 
        # characterin the string
        strMax = 0
        
        for ch in range('a','z'):
            strMax = max(strMax, 
                     freq[chr(ch)])

        # Update the answer
        ans = ans - strMax

    return ans

# Driver Code
str = "geeksgeeks"
print(getMinimumRemoval(str))

# This code is contributed by avanitrachhadiya2155