Delete as few characters as possible from s so that every remaining letter has a different frequency. Only letters still present matter: several letters may be deleted entirely. Return the minimum number of deletions.
Example 1:
Input: s = "aabb"
Output: 1Explanation: Both letters initially occur twice. Delete one occurrence of either letter to obtain positive frequencies 2 and 1.
Example 2:
Input: s = "aaabbc"
Output: 0Explanation: The positive frequencies are already 3 for a, 2 for b, and 1 for c. They are all distinct.
Example 3:
Input: s = "abcd"
Output: 3Explanation: Each of four letters occurs once. Keep one letter and delete the other three so that only one positive frequency remains.
Constraints:
1 <= s.length <= 100000- Only lowercase English letters occur.