class Solution {
public:
    int countBinarySubstrings(string s) {
        vector<int> count;
        int cnt = 1;
        if(s.size() == 0)    return 0;
        char last = s[0];
        for(int i = 1; i < s.size(); i ++ ){
            if(s[i] == last)    cnt ++ ;
            else{
                count.push_back(cnt);
                last = s[i];
                cnt = 1;
            }
        }
        count.push_back(cnt);
        int res =0;
        for(int i = 1; i < count.size(); i ++ ){
            res += min(count[i], count[i - 1]);
        }
        return res;
    }
};