1647. Minimum Deletions to Make Character Frequencies Unique
Description
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
.
Example 1:
Input: s = "aab"
Output: 0
Explanation: s
is already good.
Example 2:
Input: s = "aaabbbcc" Output: 2 Explanation: You can delete two 'b's resulting in the good string "aaabcc". Another way it to delete one 'b' and one 'c' resulting in the good string "aaabbc".
Example 3:
Input: s = "ceabaacb" Output: 2 Explanation: You can delete both 'c's resulting in the good string "eabaab". Note that we only care about characters that are still in the string at the end (i.e. frequency of 0 is ignored).
Constraints:
1 <= s.length <= 105
s
contains only lowercase English letters.
Solutions
Solution: Hash Map
- Time complexity: O(nlogn)
- Space complexity: O(n)
JavaScript
js
/**
* @param {string} s
* @return {number}
*/
const minDeletions = function (s) {
const charMap = {};
for (const char of s) {
charMap[char] = (charMap[char] ?? 0) + 1;
}
const frequencies = Object.values(charMap);
frequencies.sort((a, b) => b - a);
return frequencies.reduce((result, frequency, index) => {
if (index === 0) return result;
const diff = frequencies[index - 1] - frequency;
if (diff <= 0) {
const deletion = frequencies[index - 1] === 0 ? frequency : 1 - diff;
frequencies[index] -= deletion;
return result + deletion;
}
return result;
}, 0);
};