public class Solution
extends Object
2405 - Optimal Partition of String\.
Medium
Given a string `s`, partition the string into one or more **substrings** such that the characters in each substring are **unique**. That is, no letter appears in a single substring more than **once**.
Return _the **minimum** number of substrings in such a partition._
Note that each character should belong to exactly one substring in a partition.
**Example 1:**
**Input:** s = "abacaba"
**Output:** 4
**Explanation:**
Two possible partitions are ("a","ba","cab","a") and ("ab","a","ca","ba").
It can be shown that 4 is the minimum number of substrings needed.
**Example 2:**
**Input:** s = "ssssss"
**Output:** 6
**Explanation:**
The only valid partition is ("s","s","s","s","s","s").
**Constraints:**
* 1 <= s.length <= 105
* `s` consists of only English lowercase letters.