Maximize the Number of Partitions After Operations

Hard

You receive a string s and an integer k.

First, you are allowed to change at most one index in s to another lowercase English letter.

After that, do the following partitioning operation until s is empty:

Choose the longest prefix of s containing at most k distinct characters.
Delete the prefix from s and increase the number of partitions by one. The remaining characters (if any) in s maintain their initial order.

Produce an integer denoting the maximum number of resulting partitions after the operations by optimally choosing at most one index to change.

Example 1

Input: s = "accca", k = 2

Output: 3

Explanation: The optimal way is to change s[2] to something other than a and c, for example, b. then it becomes "acbca".

Then we perform the operations:

The longest prefix containing at most 2 distinct characters is "ac", we remove it and s becomes "bca".
Now The longest prefix containing at most 2 distinct characters is "bc", so we remove it and s becomes "a".
Finally, we remove "a" and s becomes empty, so the procedure ends.

Doing the operations, the string is divided into 3 partitions, so the answer is 3.

Example 2

Input: s = "aabaab", k = 3

Output: 1

Explanation: Initially s has 2 distinct characters, so whichever character we change, it will contain at most 3 distinct characters, so the longest prefix with at most 3 distinct characters would always be all of it, therefore the answer is 1.

Example 3

Input: s = "xxyz", k = 1

Output: 4

Explanation: The optimal way is to change s[0] or s[1] to something other than characters in s, for example, to change s[0] to w.

Then s becomes "wxyz", which is made of 4 distinct characters, so as k is 1, it will divide into 4 partitions.

Maximize the Number of Partitions After Operations

Constraints

Did this problem appear in one of your interviews?

Acceptance rate: 0%