Smallest K-Length Subsequence With Occurrences of a Letter
You are given a string s, an integer k, a letter letter, and an integer repetition.
Return the lexicographically smallest subsequence of s of length k that has the letter letter appear at least repetition times. The test cases are generated so that the letter appears in s at least repetition times.
A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.
A string a is lexicographically smaller than a string b if, in the first position where a and b differ, string a has a letter that appears earlier in the alphabet than the corresponding letter in b.
Example 1
Input
s = "leet", k = 3, letter = "e", repetition = 1Output
"eet"Among all length-3 subsequences of
s containing at least one e, eet is lexicographically smallest.Example 2
Input
s = "leetcode", k = 4, letter = "e", repetition = 2Output
"ecde"ecde is the lexicographically smallest subsequence of length 4 that has the letter e appear at least 2 times.Constraints
- 1 <= repetition <= k <= s.length <= 5 * 10^4
- s consists of lowercase English letters.
- letter is a lowercase English letter, and appears in s at least repetition times.