Minimum Window Substring.txt

class Solution {
public:
    string minWindow(string S, string T) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> tuse(255, 0), suse(255, 0);
        vector<char> tcha;
        string ret;
        int tsize = T.size(), ssize = S.size(), snum = 0, l = -1, i = 0, w = INT_MAX;
        if (!tsize || !ssize || (tsize > ssize))
            return "";
        for (int i = 0; i < tsize; i++) {
            tuse[T[i]]++;
            if (tuse[T[i]] == 1)
                tcha.push_back(T[i]);
        }
        while (i < ssize) {
            if (tuse[S[i]] != 0) {
                l = (l == -1)?i:l;
                suse[S[i]]++;
                snum++;
                if (tuse[S[i]] < suse[S[i]]) {
                    while(true) {
                        if (tuse[S[l]] == 0)
                            l++;
                        else if (tuse[S[l]] < suse[S[l]]) {
                            suse[S[l]]--;
                            snum--;
                            l++;
                        } else
                            break;
                    }
                }
                if ((snum >= tsize) && check(tuse, suse, tcha) && (w > (i - l + 1))) {
                    w = i - l + 1;
                    ret = S.substr(l, w);
                }
            }
            i++;
        }
        return ret;   
    }
    bool check(vector<int>& t, vector<int>& s, vector<char>& c) {
        for (size_t i = 0; i < c.size(); i++)
            if (t[c[i]] > s[c[i]])
                return false;
        return true;
    }
};