Count and Say

最新推荐文章于 2024-12-21 10:31:21 发布

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最新推荐文章于 2024-12-21 10:31:21 发布

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本文链接：https://blog.youkuaiyun.com/zzyafyj/article/details/41651297

本文详细解析了TheCount-and-Say序列的生成原理，并通过代码实现展示了如何生成序列的第n项。

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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 n^th sequence.

Note: The sequence of integers will be represented as a string

class Solution {
public:
    string countAndSay(int n) {
        string s=this->itoa(1);//第一个
        for(int i=2;i<=n;++i){//从第二个开始
            s = nextNum(s);
        }
        return s;
    }
private:
   string itoa(int i){
       char buf[10];
       memset(buf,0,sizeof(buf));
       sprintf(buf,"%d",i);
       string s(buf);
       return s;
   }
   string nextNum(string &s){
       string res;
       int j=1,count =1;
       for(;j<s.size();++j){
              if(s[j] == s[j-1]) ++count;
              else{
                  res.push_back('0'+count);
                  res.push_back(s[j-1]);
                  count=1;
              }
       }
       res.push_back('0'+count);
       res.push_back(s[j-1]);
       return res;
   }
};