#3445 -- need to fix tle

gistfile1.txt

class Solution {
public:
    int maxDifference(string s, int k) {
        int maxDiff = INT_MIN;
        int n = s.size();

        for (int win = k; win <= n; ++win) {
            unordered_map<char, int> freq;

            for (int i = 0; i < win; ++i) {
                freq[s[i]]++;
            }

            for (auto& a : freq) {
                if (a.second % 2 == 1) {
                    for (auto& b : freq) {
                        if (b.second % 2 == 0) {
                            maxDiff = max(maxDiff, a.second - b.second);
                        }
                    }
                }
            }

            for (int i = win; i < n; ++i) {
                freq[s[i - win]]--;
                if (freq[s[i - win]] == 0) {
                    freq.erase(s[i - win]);
                }
                freq[s[i]]++;

                for (auto& a : freq) {
                    if (a.second % 2 == 1) {
                        for (auto& b : freq) {
                            if (b.second % 2 == 0) {
                                maxDiff = max(maxDiff, a.second - b.second);
                            }
                        }
                    }
                }
            }
        }
        return maxDiff;
            }
};