Minimum Deletions to Make Character Frequencies Unique

1647. Minimum Deletions to Make Character Frequencies Unique A string s is called good if there are no two different characters in s that have the same frequency.

Given a string s, return the minimum number of characters you need to delete to make s good.

The frequency of a character in a string is the number of times it appears in the string. For example, in the string “aab”, the frequency of ‘a’ is 2, while the frequency of ‘b’ is 1.

Solution

1. Count the number of occurrences of the characters in the string.

2. Note the visited number.

3. Find the previous unvisited number.

   If the number if 0, it means that we have removed the characters. Thus we should NOT add 0 to visited.

def minDeletions(self, s):
    """
    :type s: str
    :rtype: int
    """
    dic = collections.Counter(s)
    
    res = 0
    visited = set()
    # print(unvisited)
    for k, v in dic.items():
        while v in visited:
            v -= 1
            res += 1
        if v != 0:
            visited.add(v)
        # print(k, v, unvisited)
    return res