Leetcode：38. Count and Say（JAVA）

【问题描述】

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.
【思路】

没有使用什么技巧，两层循环，1到n循环，内层依次扫描上一层数字。

【code】

public class Solution {
public String countAndSay(int n) {
if (n < 0) {
return null;
}
String result = "1";
StringBuffer sb = null;
if (n == 1) {
return result;
} else {
for (int i = 2; i <= n; i++) {
sb = new StringBuffer();
int count = 0;
char c = result.charAt(0);
for (int j = 0; j < result.length(); j++) {
if (result.charAt(j) == c) {
count++;
} else {
sb.append(count);
sb.append(c);
c = result.charAt(j);
count = 1;
}
}
sb.append(count);
sb.append(c);
result = sb.toString();
}
}
return result;
}
}