1525

class Solution {
public:

int numSplits(string s) {
    int n = s.size();
    
    // Prefix array to store the count of unique characters from the beginning of the string
    vector<int> prefixCount(n, 0);
    set<char> uniqueChars;

    for (int i = 0; i < n; i++) {
        uniqueChars.insert(s[i]);
        prefixCount[i] = uniqueChars.size();
    }

    // Suffix array to store the count of unique characters from the end of the string
    vector<int> suffixCount(n, 0);
    uniqueChars.clear();

    for (int i = n - 1; i > 0; i--) {
        uniqueChars.insert(s[i]);
        suffixCount[i - 1] = uniqueChars.size();
    }

    // Count the number of splits
    int ans = 0;
    for (int i = 0; i < n - 1; i++) {
        if (prefixCount[i] == suffixCount[i]) {
            ans++;
        }
    }

    return ans;
}



};