Find the Most Frequent Character with a Tie-Breaker

Question

This question asks the candidate to write a function that identifies the most frequent character in a given string, with a specific rule for tie-breaking based on alphabetical order.

Codemia · Accepted Answer

To solve the problem of finding the most frequent character with a tie-breaker, I will use a dictionary to count the occurrences of each character. After counting, I will iterate through the dictionary to determine the character with the highest frequency. In the case of a tie, I will select the character that comes first alphabetically.

1. Initialize an empty dictionary to hold character counts.
2. Loop through each character in the string and update the count in the dictionary.
3. Initialize variables to track the most frequent character and its count.
4. Iterate through the dictionary to find the character with the highest count, applying the tie-breaking rule.
5. Return the most frequent character.

The time complexity of this solution is O(n), where n is the length of the input string, since we traverse the string and the dictionary once. The space complexity is O(k), where k is the number of unique characters in the string, as we store counts for each character.

Here is a Python implementation of the solution:
```python
def most_frequent_char(s):
    char_count = {}
    for char in s:
        if char in char_count:
            char_count[char] += 1
        else:
            char_count[char] = 1

most_frequent = ''
    max_count = 0
    for char, count in char_count.items():
        if count > max_count or (count == max_count and char < most_frequent):
            most_frequent = char
            max_count = count

return most_frequent
```
This code efficiently counts characters and applies the tie-breaking rule.

It is important to handle edge cases, such as an empty string, where the function should return None or an appropriate message. Additionally, if all characters are unique, the function should return the first character in the string.

Find the Most Frequent Character with a Tie-Breaker

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