算法第15周Count and Say[easy]

Description

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

1.     12.     113.     214.     12115.     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 term of the count-and-say sequence.

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

Example 1:

Input: 1Output: "1"

Example 2:

Input: 4Output: "1211"

---

Solution

通过题目要求，我们不难发现他的下一个字符串就是根据上一个字符串得到，注意是计算连续的数字有几个然后作为新的字符串。
我们采用for循环的方式。

class Solution {public:    string countAndSay(int n) {        string start = "1";        if (n == 1) return start;        for (int i = 1; i < n; i++) {            string temp = start;            start = "";            int len = temp.length();            int count;            for (int j = 0; j < len;) {                count = 1;                char h = temp[j];                int k = j;                while (k+1 < len&& temp[k+1] == h) {                    k++;                    count++;                }                char c = count+48;                start = start+c+h;                j = k+1;            }        }        return start;    }};