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Sort Characters By Frequency

Question​

Write a function to sort the characters in a given string in descending order based on the frequency of occurrence of each character.

Example 1
Input: "tree"
Output: "eert"

Solution​

all//Sort Characters By Frequency.py


def sort_by_frequency(string):
    # Make a dictionary of the characters in the string
    # and their respective frequencies
    char_freq = {}
    for char in string:
        if char in char_freq:
            char_freq[char] += 1
        else:
            char_freq[char] = 1

    # Sort the dictionary in descending order
    # based on character frequency
    sorted_freq = sorted(char_freq.items(), key=lambda x: x[1], reverse=True)

    # Create a new string, with characters sorted by frequency
    sorted_string = ""
    for item in sorted_freq:
        sorted_string += item[0] * item[1]

    return sorted_string

# Test
string = "tree"
print(sort_by_frequency(string)) # Output: eert