#Leetcode# 38. Count and Say

https://leetcode.com/problems/count-and-say/

 

The count-and-say sequence is the sequence of integers with the first five terms as following:

1.     1
2.     11
3.     21
4.     1211
5.     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 where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.

Note: Each term of the sequence of integers will be represented as a string.

 

Example 1:

Input: 1
Output: "1"

Example 2:

Input: 4
Output: "1211"

代码：

class Solution {
public:
    string countAndSay(int n) {
        if (n <= 0) return "";
        string res = "1";
        while (--n) {
            string cur = "";
            for (int i = 0; i < res.size(); ++i) {
                int cnt = 1;
                while (i + 1 < res.size() && res[i] == res[i + 1]) {
                    ++cnt;
                    ++i;
                }
                cur += to_string(cnt) + res[i];
            }
            res = cur;
        }
        return res;
    }
};

　　这个和 PAT 乙级里面的外观数列一样的 但四顾不是很明白题意  然而时过境迁现在也不是很清楚 猪脑子？

class Solution {public:    string countAndSay(int n) {        if (n <= 0) return "";        string res = "1";        while (--n) {            string cur = "";            for (int i = 0; i < res.size(); ++i) {                int cnt = 1;                while (i + 1 < res.size() && res[i] == res[i + 1]) {                    ++cnt;                    ++i;                }                cur += to_string(cnt) + res[i];            }            res = cur;        }        return res;    }};