1525. Number of Good Ways to Split a String

https://leetcode.com/problems/number-of-good-ways-to-split-a-string

Description

You are given a string s, a split is called good if you can split s into 2 non-empty strings p and q where its concatenation is equal to s and the number of distinct letters in p and q are the same.

Return the number of good splits you can make in s.

Example 1:

**Input:** s = "aacaba"
**Output:** 2
**Explanation:** There are 5 ways to split "aacaba" and 2 of them are good. 
("a", "acaba") Left string and right string contains 1 and 3 different letters respectively.
("aa", "caba") Left string and right string contains 1 and 3 different letters respectively.
("aac", "aba") Left string and right string contains 2 and 2 different letters respectively (good split).
("aaca", "ba") Left string and right string contains 2 and 2 different letters respectively (good split).
("aacab", "a") Left string and right string contains 3 and 1 different letters respectively.

Example 2:

**Input:** s = "abcd"
**Output:** 1
**Explanation:** Split the string as follows ("ab", "cd").

Example 3:

**Input:** s = "aaaaa"
**Output:** 4
**Explanation:** All possible splits are good.

Example 4:

**Input:** s = "acbadbaada"

**Output:** 2

Constraints:

• s contains only lowercase English letters.

• 1 <= s.length <= 10^5

ac