lintcode-easy-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

n

th sequence.

Example

Given n =

5

, return

"111221"

.

Note

The sequence of integers will be represented as a string.

思路也很直接，但是写的时候要注意数组index越界一类的问题

public class Solution {
/**
* @param n the nth
* @return the nth sequence
*/
public String countAndSay(int n) {
// Write your code here
if(n < 1)
return null;

if(n == 1)
return "1";

String prev = "1";
String next = "";

for(int i = 2; i <= n; i++){
char[] temp = prev.toCharArray();

int index = 0;
while(index < temp.length){
int count = 0;

count++;
index++;
while(index < temp.length && temp[index] == temp[index - 1]){
count++;
index++;
}
next = next + String.valueOf(count) + temp[index - 1];
}
prev = next;
next = "";
}

return prev;
}
}