Leetcode -- Count and Say

class Solution {  
 public:  
   string countAndSay(int n) {  
     vector<string> results(n);  
     results[0] = "1";  
     for(int i = 1; i < n; ++i) {  
       results[i] = generate(results[i - 1]);  
     }  
     return results[n - 1];  
   }  
   string generate(string s) {  
     string result;  
     int i = 0;  
     while(i < s.length()) {  
       char c = s[i];  
       int j = i + 1;  
       while(j < s.length() && s[j] == c){  
         j++;  
       };  
       result += to_string(j - i) + c;  
       i = j;  
     }  
     return result;  
   }  
 };