1647. Minimum Deletions to Make Character Frequencies Unique

1647. Minimum Deletions to Make Character Frequencies Unique #

题目 #

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.

题目大意 #

如果字符串 s 中 不存在 两个不同字符 频次 相同的情况,就称 s 是 优质字符串 。

给你一个字符串 s,返回使 s 成为优质字符串需要删除的最小字符数。

字符串中字符的 频次 是该字符在字符串中的出现次数。例如,在字符串 “aab” 中,‘a’ 的频次是 2,而 ‘b’ 的频次是 1 。

提示:

  • 1 <= s.length <= 105
  • s 仅含小写英文字母

解题思路 #

  • 给出一个字符串 s,要求输出使 s 变成“优质字符串”需要删除的最小字符数。“优质字符串”的定义是:字符串 s 中不存在频次相同的两个不同字符。
  • 首先将 26 个字母在字符串中的频次分别统计出来,然后把频次从大到小排列,从频次大的开始,依次调整:例如,假设前一个和后一个频次相等,就把前一个字符删除一个,频次减一,再次排序,如果频次还相等,继续调整,如果频次不同了,游标往后移,继续调整后面的频次。直到所有的频次都不同了,就可以输出最终结果了。
  • 这里需要注意频次为 0 的情况,即字母都被删光了。频次为 0 以后,就不需要再比较了。

代码 #

package leetcode

import (
	"sort"
)

func minDeletions(s string) int {
	frequency, res := make([]int, 26), 0
	for i := 0; i < len(s); i++ {
		frequency[s[i]-'a']++
	}
	sort.Sort(sort.Reverse(sort.IntSlice(frequency)))
	for i := 1; i <= 25; i++ {
		if frequency[i] == frequency[i-1] && frequency[i] != 0 {
			res++
			frequency[i]--
			sort.Sort(sort.Reverse(sort.IntSlice(frequency)))
			i--
		}
	}
	return res
}
Calendar Nov 24, 2020
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