LeetCode-in-Java
1525. Number of Good Ways to Split a String
Medium
You are given a string s.
A split is called good if you can split s into two non-empty strings sleft and sright where their concatenation is equal to s (i.e., sleft + sright = s) and the number of distinct letters in sleft and sright is 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”).
Constraints:
1 <= s.length <= 105sconsists of only lowercase English letters.
Solution
import java.util.HashSet;
public class Solution {
public int numSplits(String s) {
HashSet<Character> hs = new HashSet<>();
int[] dp1 = new int[s.length() - 1];
int[] dp2 = new int[s.length() - 1];
for (int i = 0; i < s.length() - 1; i++) {
char ch = s.charAt(i);
hs.add(ch);
dp1[i] = hs.size();
}
HashSet<Character> hm = new HashSet<>();
for (int i = s.length() - 1; i > 0; i--) {
char ch = s.charAt(i);
hm.add(ch);
dp2[i - 1] = hm.size();
}
int count = 0;
for (int i = 0; i < s.length() - 1; i++) {
if (dp1[i] == dp2[i]) {
count++;
}
}
return count;
}
}