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 where 1 ≤ n ≤ 30, 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"
class Solution { public String countAndSay(int n) { StringBuilder sb1 = new StringBuilder("1"), sb2 = sb1; while(--n > 0){ sb2 = new StringBuilder(); int c = 1, i = 0; char[] ch = sb1.toString().toCharArray(); while(i < sb1.length()){ if(i+1 < sb1.length() && ch[i] == ch[i+1]) ++c; else{ sb2.append(c).append(ch[i]); c = 1; } ++i; } sb1 = sb2; } return sb2.toString(); } }
来自leetcode，高效简洁
原文：https://www.cnblogs.com/wentiliangkaihua/p/10336371.html