You are given a 0-indexed string s and an integer k.
You are to perform the following partitioning operations until s is empty:
s containing at most k distinct characters.s and increase the number of partitions by one. The remaining characters (if any) in s maintain their initial order.Before the operations, you are allowed to change at most one index in s to another lowercase English letter.
Return an integer denoting the maximum number of resulting partitions after the operations by optimally choosing at most one index to change.
\n\n
Example 1:
\n\n\nInput: s = "accca", k = 2\nOutput: 3\nExplanation: In this example, to maximize the number of resulting partitions, s[2] can be changed to 'b'.\ns becomes "acbca".\nThe operations can now be performed as follows until s becomes empty:\n- Choose the longest prefix containing at most 2 distinct characters, "acbca".\n- Delete the prefix, and s becomes "bca". The number of partitions is now 1.\n- Choose the longest prefix containing at most 2 distinct characters, "bca".\n- Delete the prefix, and s becomes "a". The number of partitions is now 2.\n- Choose the longest prefix containing at most 2 distinct characters, "a".\n- Delete the prefix, and s becomes empty. The number of partitions is now 3.\nHence, the answer is 3.\nIt can be shown that it is not possible to obtain more than 3 partitions.\n\n
Example 2:
\n\n\nInput: s = "aabaab", k = 3\nOutput: 1\nExplanation: In this example, to maximize the number of resulting partitions we can leave s as it is.\nThe operations can now be performed as follows until s becomes empty: \n- Choose the longest prefix containing at most 3 distinct characters, "aabaab".\n- Delete the prefix, and s becomes empty. The number of partitions becomes 1. \nHence, the answer is 1. \nIt can be shown that it is not possible to obtain more than 1 partition.\n\n\n
Example 3:
\n\n\nInput: s = "xxyz", k = 1\nOutput: 4\nExplanation: In this example, to maximize the number of resulting partitions, s[1] can be changed to 'a'.\ns becomes "xayz".\nThe operations can now be performed as follows until s becomes empty:\n- Choose the longest prefix containing at most 1 distinct character, "xayz".\n- Delete the prefix, and s becomes "ayz". The number of partitions is now 1.\n- Choose the longest prefix containing at most 1 distinct character, "ayz".\n- Delete the prefix, and s becomes "yz". The number of partitions is now 2.\n- Choose the longest prefix containing at most 1 distinct character, "yz".\n- Delete the prefix, and s becomes "z". The number of partitions is now 3.\n- Choose the longest prefix containing at most 1 distinct character, "z".\n- Delete the prefix, and s becomes empty. The number of partitions is now 4.\nHence, the answer is 4.\nIt can be shown that it is not possible to obtain more than 4 partitions.\n\n\n
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Constraints:
\n\n1 <= s.length <= 104s consists only of lowercase English letters.1 <= k <= 26给你一个下标从 0 开始的字符串 s 和一个整数 k。
你需要执行以下分割操作，直到字符串 s 变为 空：
s 的最长前缀，该前缀最多包含 k 个 不同 字符。s 中保持原来的顺序。执行操作之 前 ，你可以将 s 中 至多一处 下标的对应字符更改为另一个小写英文字母。
在最优选择情形下改变至多一处下标对应字符后，用整数表示并返回操作结束时得到的最大分割数量。
\n\n\n\n
示例 1：
\n\n\n输入：s = \"accca\", k = 2\n输出：3\n解释：在此示例中，为了最大化得到的分割数量，可以将 s[2] 改为 'b'。\ns 变为 \"acbca\"。\n按照以下方式执行操作，直到 s 变为空：\n- 选择最长且至多包含 2 个不同字符的前缀，\"acbca\"。\n- 删除该前缀，s 变为 \"bca\"。现在分割数量为 1。\n- 选择最长且至多包含 2 个不同字符的前缀，\"bca\"。\n- 删除该前缀，s 变为 \"a\"。现在分割数量为 2。\n- 选择最长且至多包含 2 个不同字符的前缀，\"a\"。\n- 删除该前缀，s 变为空。现在分割数量为 3。\n因此，答案是 3。\n可以证明，分割数量不可能超过 3。\n\n
示例 2：
\n\n\n输入：s = \"aabaab\", k = 3\n输出：1\n解释：在此示例中，为了最大化得到的分割数量，可以保持 s 不变。\n按照以下方式执行操作，直到 s 变为空： \n- 选择最长且至多包含 3 个不同字符的前缀，\"aabaab\"。\n- 删除该前缀，s 变为空。现在分割数量为 1。\n因此，答案是 1。\n可以证明，分割数量不可能超过 1。\n\n
示例 3：
\n\n\n输入：s = \"xxyz\", k = 1\n输出：4\n解释：在此示例中，为了最大化得到的分割数量，可以将 s[1] 改为 'a'。\ns 变为 \"xayz\"。\n按照以下方式执行操作，直到 s 变为空：\n- 选择最长且至多包含 1 个不同字符的前缀，\"xayz\"。\n- 删除该前缀，s 变为 \"ayz\"。现在分割数量为 1。\n- 选择最长且至多包含 1 个不同字符的前缀，\"ayz\"。\n- 删除该前缀，s 变为 \"yz\"，现在分割数量为 2。\n- 选择最长且至多包含 1 个不同字符的前缀，\"yz\"。\n- 删除该前缀，s 变为 \"z\"。现在分割数量为 3。\n- 选择最且至多包含 1 个不同字符的前缀，\"z\"。\n- 删除该前缀，s 变为空。现在分割数量为 4。\n因此，答案是 4。\n可以证明，分割数量不可能超过 4。\n\n
\n\n
提示：
\n\n1 <= s.length <= 104s 只包含小写英文字母。1 <= k <= 26pref[i]: The number of resulting partitions from the operations by performing the operations on s[0:i].suff[i]: The number of resulting partitions from the operations by performing the operations on s[i:n - 1], where n == s.length.partition_start[i]: The start index of the partition containing the ith index after performing the operations.i, we can try all possible 25 replacements:r, such that the number of distinct characters in the range [partition_start[i], r] is at most k.2 cases:r >= i: the number of resulting partitions in this case is 1 + pref[partition_start[i] - 1] + suff[r + 1].r2 such that the number of distinct characters in the range [r:r2] is at most k. The answer in this case is 2 + pref[partition_start[i] - 1] + suff[r2 + 1]\\u7248\\u672c\\uff1a \\u7f16\\u8bd1\\u65f6\\uff0c\\u5c06\\u4f1a\\u91c7\\u7528 \\u4e3a\\u4e86\\u4f7f\\u7528\\u65b9\\u4fbf\\uff0c\\u5927\\u90e8\\u5206\\u6807\\u51c6\\u5e93\\u7684\\u5934\\u6587\\u4ef6\\u5df2\\u7ecf\\u88ab\\u81ea\\u52a8\\u5bfc\\u5165\\u3002<\\/p>\"],\"java\":[\"Java\",\" \\u7248\\u672c\\uff1a \\u4e3a\\u4e86\\u65b9\\u4fbf\\u8d77\\u89c1\\uff0c\\u5927\\u90e8\\u5206\\u6807\\u51c6\\u5e93\\u7684\\u5934\\u6587\\u4ef6\\u5df2\\u88ab\\u5bfc\\u5165\\u3002<\\/p>\\r\\n\\r\\n \\u5305\\u542b Pair \\u7c7b: https:\\/\\/docs.oracle.com\\/javase\\/8\\/javafx\\/api\\/javafx\\/util\\/Pair.html <\\/p>\"],\"python\":[\"Python\",\" \\u7248\\u672c\\uff1a \\u4e3a\\u4e86\\u65b9\\u4fbf\\u8d77\\u89c1\\uff0c\\u5927\\u90e8\\u5206\\u5e38\\u7528\\u5e93\\u5df2\\u7ecf\\u88ab\\u81ea\\u52a8 \\u5bfc\\u5165\\uff0c\\u5982\\uff1aarray<\\/a>, bisect<\\/a>, 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