leetcode: count and say

最新推荐文章于 2022-01-10 20:06:35 发布

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#leetcode #count #say #c++

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本文介绍了一种生成计数读数序列的方法，通过解析序列的构造规则，使用C++实现了一个递归算法来生成任意指定位置的序列。计数读数序列是一种特殊的整数序列，从1开始，每一项都是对其前一项的描述。

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.

class Solution {
public:
    string countAndSay(int n) {
        if (n < 0)
            return NULL;
        if (n == 0)
            return "1";
        string s = "1";
        string tmp = "";
        char c1;
        char cc;
        int count = 0;

        for(int i = 1; i < n; i++){
            c1 = s[0];
            count = 1;
            for(int j = 1; j < s.length(); j++){
                if(s[j] != c1){
                    cc =  count+'0';  
                    tmp = tmp + cc + c1;                   
                    c1 = s[j];
                    count = 1;
                }
                else 
                    count++;                
            }
            cc =  count+'0';  
            tmp = tmp + cc + c1;
            s = tmp;
            tmp = "";
        }
        return s;
    }
};