LeetCode 115 Count and Say

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.

分析：

根据指定好的规则，一条一条构造，直到第n个输出。

public class Solution {
public String countAndSay(int n) {
if(n==1) return "1";
String s = "1";//第一个是构造后面的基础
int round=1;
int count=0;
int i=0;
StringBuffer sb = new StringBuffer();
while(round < n){
count = 1;
sb.setLength(0);//清零
for(i=1; i<s.length(); i++){
if(s.charAt(i)==s.charAt(i-1))
count++;
else{
sb.append(count).append(s.charAt(i-1));
count=1;
}
}
sb.append(count).append(s.charAt(i-1));
s = sb.toString();
round++;
}
return s;
}
}