38. Count and Say

Problem: The count-and-say sequence is the sequence of integers with the first five terms as following:

1.     1

2.     11
3.     21

4.     1211

5.     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 term of the count-and-say sequence.

Note: Each term of the sequence of integers will be represented as a string.

Example 1:

Input: 1

Output: "1"

Example 2:

Input: 4

Output: "1211" 

Approach: The solution is straight forward. The appendNext method is run over n times where n is the input.

class Solution {
public:
    public:
 
    string appendNext(string str){
        string str1;
        char ch = str[0];
        int chCount = 1;
        for(int i = 1; i <= str.size(); i++){
            if (str[i] == ch){
                chCount++;
            }
            else {
                char chr = chCount + '0';
                str1 = str1 + chr;
                str1 = str1 + ch;
                ch = str[i];
                chCount = 1;
            }
        }
        return str1;
    }
    
    string countAndSay(int n) {
        if (n == 1) {
            return "1";
        }
        string str1 = "1";
        string strn;
        for (int i = 1; i < n; i++){
            strn = appendNext(str1);
            str1 = strn;
        }
        return strn;
    }
};

Here is the link to the ideone solution : http://ideone.com/tbYXUM