Solution2.cpp

class Solution {
public:
    vector<int> findAnagrams(string s, string p) {
        int m = s.size(), n = p.size();
        vector<int> ans;
        if (m < n) {
            return ans;
        }
        vector<int> cnt1(26);
        for (char& c : p) {
            ++cnt1[c - 'a'];
        }
        vector<int> cnt2(26);
        for (int i = 0, j = 0; i < m; ++i) {
            int k = s[i] - 'a';
            ++cnt2[k];
            while (cnt2[k] > cnt1[k]) {
                --cnt2[s[j++] - 'a'];
            }
            if (i - j + 1 == n) {
                ans.push_back(j);
            }
        }
        return ans;
    }
};