The count-and-say sequence is the sequence of integers with the first five terms as following:
111211211111221
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.
Example：
Input: 1
Output: "1"
Input: 4
Output: "1211"
解释下题目：
这道题目看了半天没看懂，其实就是说让你读前面一串数字，比如5=111221，意思就是代表4的那一串有一个1(
11)，一个2(12)和两个1(21)
1. 递归
实际耗时：2ms
public String countAndSay(int n) {
if (n <= 0) {
return "";
}
if (1 == n) {
return "1";
}
if (2 == n) {
return "11";
} else {
//递归实现
String str = countAndSay(n - 1);
StringBuilder stringBuilder = new StringBuilder();
char[] a = str.toCharArray();
int count = 1;
for (int i = 0; i < a.length - 1; i++) {
if (a[i] == a[i + 1]) {
count++;
} else {
stringBuilder.append(count).append(a[i]);
count = 1;
}
}
stringBuilder.append(count).append(a[a.length - 1]);
return stringBuilder.toString();
}
}
思路很简单，就是老老实实读呗。
