LeetCode in Kotlin
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 -
scontains only lower case English letters.
Solution
class Solution {
fun maxUniqueSplit(s: String): Int {
var lo = 1
var hi = s.length
// binary search
while (lo < hi) {
val mid = lo + hi + 1 shr 1
if (ok(0, mid, 0, s, HashSet())) {
lo = mid
} else {
hi = mid - 1
}
}
return lo
}
private fun ok(depth: Int, end: Int, curLen: Int, s: String, seen: MutableSet<String>): Boolean {
if (depth == end) {
return true
}
for (j in curLen until s.length) {
// not enough length remains to reach the end.
if (s.length - j < end - depth) {
break
}
val cur = s.substring(curLen, j + 1)
if (seen.add(cur)) {
if (ok(depth + 1, end, j + 1, s, seen)) {
return true
}
seen.remove(cur)
}
}
return false
}
}