【leetcode】38-Count and Say

problem

Count and Say

xiangjian Look-and-say sequence

https://en.wikipedia.org/wiki/Look-and-say_sequence

 code

class Solution {
public:
    string countAndSay(int n) {
        if(n<1) return "";
        string res = "1";
        string tmp;
        for(int i=1; i<n; i++)//run from starting to generate second string.
        {
            int len = res.size();
            for(int j=0; j<len; j++)//check all digits in the string.
            {
                int count = 1;//we have at least 1 occurrence of each digit.
                while((j+1<len)&&(res[j]==res[j+1]))//get the number of times same digit occured.
                {
                    count++;
                    j++;//keep increasing the index inside of the string.
                    
                }
                tmp += to_string(count) + res[j];//add to new string "count"+"digit".
                
            }
            res = tmp;//save string result.
            tmp.clear();//clear string-helper.
            
        }
        return res;
        
    }
};

 

 

 

 

参考

1.leetcode;

完