CountAndSay.java

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

/*Prateekshya's Solution*/

class Solution {
    public String countAndSay(int n) {
        if (n == 1) return "1";
        StringBuilder str = new StringBuilder("1");
        while (n > 1)
        {
            StringBuilder say = new StringBuilder("");
            int count = 0;
            char curr = '0';
            for (int i = 0; i < str.length(); ++i)
            {
                //if current character is not same as the previous
                if (curr != str.charAt(i))
                {
                    //update the say
                    if (curr != '0')
                    {
                        say.append(count);
                        say.append(curr);
                    }

                    //update the curr and count
                    curr = str.charAt(i);
                    count = 1;
                }

                //if same then increment count
                else
                {
                    ++count;
                }
            }

            //update the say
            if (curr != '0')
            {
                say.append(count);
                say.append(curr);
            }

            //store it as str for next iteration
            str = new StringBuilder(say);

            //decrease n
            --n;
        }
        return new String(str);
    }
}

/*Pratik's Solution*/

class Solution {
    public String countAndSay(int n) 
    {
        if(n==1)return "1";
        if(n==2)return "11";
        return count(countAndSay(n-1));
    }
    public String count(String s)
    {
        int count = 1;
        String res = new String();
        for(int i=0;i<s.length()-1;i++)
        {
            if(s.charAt(i)==s.charAt(i+1))
            {
                count++;
            }
            else
            {
                String c = String.valueOf(count);
                res+=c;
                res+=s.charAt(i);
                count = 1;
            }
        }
        if(s.charAt(s.length()-1)==s.charAt(s.length()-2))
        {
            res+=String.valueOf(count);
            res+=s.charAt(s.length()-1);
        }
        else
        {
            res+='1';
            res+=s.charAt(s.length()-1);
        }
        return res;
    }
}