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Check if All Characters Have Equal Number of Occurrences

Difficulty: Easy

Problem Description

Given a string s, return true if s is a good string, or false otherwise. A string s is good if all the characters that appear in s have the same number of occurrences (i.e., the same frequency).

Key Insights

  • The problem requires counting the frequency of each character in the string.
  • A good string has all characters with the same frequency.
  • Efficient counting can be done using a hash table (or dictionary).
  • We need to compare the frequencies of characters to determine if they are all equal.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the string s, as we need to traverse the string to count characters. Space Complexity: O(1), since the number of unique characters is limited (26 lowercase English letters).

Solution

To solve the problem, we can use a hash table to count the occurrences of each character in the string. After counting, we check if all values in the hash table are the same. If they are, we return true, otherwise false.

  1. Initialize a hash table (dictionary) to store character counts.
  2. Traverse each character in the string, updating the count in the hash table.
  3. Retrieve the unique frequencies of the counts and check if there is only one unique frequency.
  4. Return true if there is one unique frequency, otherwise false.

Code Solutions

def areOccurrencesEqual(s: str) -> bool:
    from collections import Counter
    count = Counter(s)  # Count the frequency of each character
    frequencies = set(count.values())  # Get the unique frequencies
    return len(frequencies) == 1  # Check if there is only one unique frequency
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