LeetCode [1593] Split a String Into the Max Number of Unique Substrings

 1593. Split a String Into the Max Number of Unique Substrings

Medium

Given a string s, return the maximum number of unique substrings that the given string can be split into.

You can split string s into any list of non-empty substrings, where the concatenation of the substrings forms the original string. However, you must split the substrings such that all of them are unique.

A substring is a contiguous sequence of characters within a string.

 

Example 1:

Input: s = "ababccc"
Output: 5
Explanation: One way to split maximally is ['a', 'b', 'ab', 'c', 'cc']. Splitting like ['a', 'b', 'a', 'b', 'c', 'cc'] is not valid as you have 'a' and 'b' multiple times.

Example 2:

Input: s = "aba"
Output: 2
Explanation: One way to split maximally is ['a', 'ba'].

Example 3:

Input: s = "aa"
Output: 1
Explanation: It is impossible to split the string any further.

 

Constraints:

• 1 <= s.length <= 16

• s contains only lower case English letters.

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class Solution { int r = 0; public int maxUniqueSplit(String s) { dfs(0, s.length(), s, new HashSet<>()); return r; } void dfs(int i, int n, String s, Set<String> set){ if(i==n){ r = Math.max(r, set.size()); }else{ for(int j=i; j<n; ++j){ String sb = s.substring(i, j+1); if(!set.contains(sb)){ set.add(sb); dfs(j+1, n, s, set); set.remove(sb); } } } } }