Leetcode Count and Say

The count-and-say sequence is the sequence of integers beginning as follows:
1, 11, 21, 1211, 111221, ...

1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.

Given an integer n, generate the nth sequence.

Note: The sequence of integers will be represented as a string.

遞推即可，

每count and say一次，統計字串中連續字元出現的次數，然後將其轉化成字串即可

class Solution {
public:
    string countAndSay(int n) {
        string init = "1";
        for(int i = 1 ; i < n ; ++ i){
            int cnt =1;
            char pre = init[0];
            string str = "";
            for(int j = 1 ; j <  init.length(); ++ j){
                if(init[j]!=pre){
                    str+=to_string(cnt)+pre;
                    cnt = 1;
                    pre = init[j];
                }else{
                    cnt++;
                }
            }
            str+=to_string(cnt)+pre;
            init = str;
        }
        return init;
    }
};