[Swift]LeetCode1297. 子串的最大出现次数 | Maximum Number of Occurrences of a Substring
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Given a string s, return the maximum number of ocurrences of any substring under the following rules:
The number of unique characters in the substring must be less than or equal to maxLetters.
The substring size must be between minSize and maxSize inclusive.
Example 1:
Input: s = "aababcaab", maxLetters = 2, minSize = 3, maxSize = 4
Output: 2
Explanation: Substring "aab" has 2 ocurrences in the original string.
It satisfies the conditions, 2 unique letters and size 3 (between minSize and maxSize).
Example 2:
Input: s = "aaaa", maxLetters = 1, minSize = 3, maxSize = 3
Output: 2
Explanation: Substring "aaa" occur 2 times in the string. It can overlap.
Example 3:
Input: s = "aabcabcab", maxLetters = 2, minSize = 2, maxSize = 3
Output: 3
Example 4:
Input: s = "abcde", maxLetters = 2, minSize = 3, maxSize = 3
Output: 0
Constraints:
1 <= s.length <= 10^5
1 <= maxLetters <= 26
1 <= minSize <= maxSize <= min(26, s.length)
s only contains lowercase English letters.
给你一个字符串 s ，请你返回满足以下条件且出现次数最大的 任意 子串的出现次数：
子串中不同字母的数目必须小于等于 maxLetters 。
子串的长度必须大于等于 minSize 且小于等于 maxSize 。
示例 1：
输入：s = "aababcaab", maxLetters = 2, minSize = 3, maxSize = 4
输出：2
解释：子串 "aab" 在原字符串中出现了 2 次。
它满足所有的要求：2 个不同的字母，长度为 3 （在 minSize 和 maxSize 范围内）。
示例 2：
输入：s = "aaaa", maxLetters = 1, minSize = 3, maxSize = 3
输出：2
解释：子串 "aaa" 在原字符串中出现了 2 次，且它们有重叠部分。
示例 3：
输入：s = "aabcabcab", maxLetters = 2, minSize = 2, maxSize = 3
输出：3
示例 4：
输入：s = "abcde", maxLetters = 2, minSize = 3, maxSize = 3
输出：0
提示：
1 <= s.length <= 10^5
1 <= maxLetters <= 26
1 <= minSize <= maxSize <= min(26, s.length)
s 只包含小写英文字母。
