CountandSay.java

package leetcode;

/**
 * Project Name : Leetcode
 * Package Name : leetcode
 * File Name : CountandSay
 * Creator : Edward
 * Date : Oct, 2017
 * Description : 38. Count and Say
 */
public class CountandSay {
    /**
     1.     1
     2.     11
     3.     21
     4.     1211
     5.     111221

     time : 不知道
     space : O(n)

     * @param n
     * @return
     */
    public String countAndSay(int n) {
        int i = 1;
        String res = "1";
        while (i < n) {
            int count = 0;
            StringBuilder sb = new StringBuilder();
            char c = res.charAt(0);
            for (int j = 0; j <= res.length(); j++) {
                if (j != res.length() && res.charAt(j) == c) {
                    count++;
                } else {
                    sb.append(count);
                    sb.append(c);
                    if (j != res.length()) {
                        count = 1;
                        c = res.charAt(j);
                    }
                }
            }
            res = sb.toString();
            i++;
        }
        return res;
    }
}