1358-number-of-substrings-containing-all-three-characters.cpp

class Solution {
public:
    int numberOfSubstrings(string s) {
        int ans = 0;
        int n = s.size();
        map<char, int> mp;
        for (int l = 0, r = 0; r < n; r++) {
            mp[s[r]]++;
            while (mp.size() == 3) {
                ans += (n - r);
                mp[s[l]]--;
                if (mp[s[l]] == 0) mp.erase(s[l]);
                l++;
            }
        }
        return ans;
    }
};