19.2.3 [LeetCode 38] 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"

题意

题意相当脑残，都没写清楚

就是n+1编号的字符串是以count-and-say形式复述编号n的字符串的结果

题解

class Solution {
public:
    string countAndSay(int n) {
        string ans = "1";
        n--;
        while (n--) {
            string tmp = "";
            int p = 0, l = ans.length();
            for (int i = 1; i < l; i++) {
                if (ans[i - 1] != ans[i]) {
                    char ch = i - p + '0';
                    tmp += ch;
                    ch = ans[i - 1];
                    tmp += ch;
                    p = i;
                }
            }
            char ch = l - p + '0';
            tmp += ch;
            ch = ans[l - 1];
            tmp += ch;
            ans = tmp;
        }
        return ans;
    }
};