class Solution {public:    int magicalString(int n) {        if(!n) return 0;        if(n < 2) return 1;                int ret = 1;        string s = "1";        bool isOne = false;        int i = 0; // num inx        while(s.length() < n)        {            int cnt = 0;            if(isOne)            {                s += ‘1‘; ret ++;                cnt = (s[++i] - ‘1‘) + 1;                if(cnt == 2 && n > s.length())                {s += ‘1‘; ret ++;}            }            else            {                s += ‘2‘;                cnt = (s[++i] - ‘1‘) + 1;                if(cnt == 2) s += ‘2‘;            }                        // move on            isOne = !isOne;        }                return ret;    }};