[Leetcode] 38. Count and Say 计数和

Related Topics：[String]
Similar Questions:[Encode and Decode Strings][String Compression]

题目：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.

这道计数和读法就是对于前一个数，找出相同元素的个数，把个数和该元素存到新的string里。代码如下:

java解法：

class Solution {
    public String countAndSay(int n) {
        if(n<=0) return "";
        String res="1";
        while(n-1>0) {
            String cur="";
            int i=0;
            while(i<res.length()) {
                int count=1;
                while((i+1)<res.length()&&res.charAt(i+1)==res.charAt(i)) {
                    count++;
                    i++;
                }
                cur+=Integer.toString(count)+res.charAt(i);
                i++;
            }
            res=cur;
            n--;
        }
        return res;
    }
}