【leetcode 滑动窗口 C++】76. Minimum Window Substring

76. Minimum Window Substring

class Solution {
    
    
public:
    int getIndex(char ch) {
    
    
        if(ch >= 'A' && ch <= 'Z') return ch - 'A';
        return ch - 'a' + 26;
    }
    string minWindow(string s, string t) {
    
    
        string ans = "";

        set<int> is_in_t;
        vector<int> t_cnt(52, 0);
        for(auto ch : t) {
    
    
            int ind = getIndex(ch);
            t_cnt[ind]++;
            is_in_t.insert(ind);
        }

        int l = 0;
        vector<int> sub_s_cnt(52, 0);
        for(int r = 0; r < s.size(); r++) {
    
    
            sub_s_cnt[getIndex(s[r])]++;
            for(int ind = getIndex(s[l]); l < r && sub_s_cnt[ind] > t_cnt[ind]; ) {
    
    
                sub_s_cnt[ind]--;
                ind = getIndex(s[++l]);
            }
            if(r >= l && r - l + 1 >= t.size()) {
    
    
                bool flag = true;
                for(set<int>::iterator it = is_in_t.begin(); it != is_in_t.end(); it++) {
    
    
                    if(sub_s_cnt[*it] < t_cnt[*it]) {
    
    
                        flag = false;
                        break;
                    }
                }
                if(flag && (!ans.size() || r - l + 1 <= ans.size())) ans = s.substr(l, r - l + 1);
            }
        }
        return ans;
    }
};