CountandSay.java

package com.fishercoder.solutions;

public class CountandSay {
/**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.*/
    public String countAndSay(int n) {
        StringBuilder curr = new StringBuilder("1");
        StringBuilder prev;
        int count;
        char say;
        for(int i = 1; i < n; i++){
            prev = curr;
            curr = new StringBuilder();
            count = 1;
            say = prev.charAt(0);
            
            for(int j = 1, len = prev.length(); j < len; j++){
                if(prev.charAt(j) != say){
                    curr.append(count).append(say);
                    count = 1;
                    say = prev.charAt(j);
                } else count++;
            }
            curr.append(count).append(say);
        }
        return curr.toString();
    }

}