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Maximum Difference Between Even and Odd Frequency I

Difficulty: Easy

Problem Description

You are given a string s consisting of lowercase English letters. Your task is to find the maximum difference between the frequency of two characters in the string such that one of the characters has an even frequency and the other character has an odd frequency. Return the maximum difference, calculated as the frequency of the character with an odd frequency minus the frequency of the character with an even frequency.

Key Insights

  • Count the frequency of each character in the string.
  • Identify characters with odd and even frequencies.
  • Calculate the maximum difference between the odd frequency and even frequency characters.
  • Ensure that the output is the difference of the maximum odd frequency and the minimum even frequency.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the string. Each character is processed once to count frequencies. Space Complexity: O(1), as the frequency count is limited to 26 lowercase English letters.

Solution

The solution involves counting the frequency of each character using a hash table (or a dictionary). We then iterate through the frequency counts to separate the characters into those with odd frequencies and those with even frequencies. Finally, we calculate the maximum difference by finding the maximum odd frequency and the minimum even frequency. The result is obtained by subtracting the minimum even frequency from the maximum odd frequency.

Code Solutions

def maxDifference(s):
    from collections import Counter

    # Count frequencies of each character
    freq = Counter(s)
    
    max_odd = float('-inf')
    min_even = float('inf')
    
    # Iterate through frequency dictionary
    for count in freq.values():
        if count % 2 == 1:  # Odd frequency
            max_odd = max(max_odd, count)
        else:  # Even frequency
            min_even = min(min_even, count)
    
    # Calculate maximum difference
    return max_odd - min_even
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