LeetCode OJ-- Count and Say

https://oj.leetcode.com/problems/count-and-say/

求经过n次变换后，变成了什么。

1  11  21  1211   111221

ps. 3 变成 ‘3’，为 3 + '0'

class Solution {
public:
    string countAndSay(int n) {
        string ans_str;
        vector<int> input;
        input.push_back(1); // the first time
        vector<int> output;
        for(int i = 1;i<n;i++)
        {
            fun(input,output);
            input = output;
        }
        
        for(int i = 0;i<input.size();i++)
            ans_str.push_back('0'+input[i]);
        return ans_str;
    }
    void fun(vector<int> input,vector<int> &output)
    {
        output.clear();
        int itr = 0;
        while(itr<input.size())
        {
            int value = input[itr];
            int times = 0;
            while(itr<input.size()&&input[itr]==value)
            {
                times++;
                itr++;
            }
            output.push_back(times);
            output.push_back(value);
        }
    }
};