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  • 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"
     

    AC code:

    class Solution {
    public:
        string countAndSay(int n) {
            vector<string> v;
            init(v, n);
            return v[n-1];
        }
        void init(vector<string>& v, int n) {
            v.push_back("1");
            for (int i = 1; i <= n; ++i) {
                string res = v[i-1];
                char c = res[0];
                string ans = "";
                int num = 1;
                for (int i = 1; i < res.length(); ++i) { 
                    if (res[i] == c) {
                        num++;
                        continue;
                    } else {
                        ans = ans + to_string(num) + c;
                        c = res[i];
                        num = 1;
                    } 
                }
                ans = ans + to_string(num) + c;
                v.push_back(ans);
            }
        }
    };
    
    Runtime: 8 ms, faster than 8.70% of C++ online submissions for Count and Say.
    永远渴望,大智若愚(stay hungry, stay foolish)
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  • 原文地址:https://www.cnblogs.com/h-hkai/p/9787086.html
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