题目描述:
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.
解题思路:
从第一个开始数起,对于输入n,则数n-1次即可。
代码如下:
public class Solution {
public String countAndSay(int n) {
int i = 1;
if (n <= 0)
return null;
String s = "1";
while (i <= n - 1) {
s = countAndSay(s);
i++;
}
return s;
} public String countAndSay(String s) {
int count = 1;
StringBuffer sb = new StringBuffer();
for (int i = 1; i < s.length(); i++) {
if (s.charAt(i - 1) == s.charAt(i))
count++;
else {
sb.append(count).append(s.charAt(i - 1));
count = 1;
}
}
sb.append(count).append(s.charAt(s.length() - 1));
return sb.toString();
}
}