LeetCode-Count and Say-优快云博客

本文链接：https://blog.youkuaiyun.com/My_Jobs/article/details/43494283

本文深入解析了计数说计数序列算法的原理与实现过程，通过逐步构建序列，展示了如何将手动计算的过程转化为计算机代码。重点讨论了两种不同的实现方式，并对比了它们的效率与清晰度，旨在帮助读者理解和掌握这一有趣的数据生成方法。

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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 nth sequence.

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

样例输出：

 1.     1
 2.     11
 3.     21
 4.     1211
 5.     111221 
 6.     312211
 7.     13112221
 8.     1113213211
 9.     31131211131221
 10.   13211311123113112211

自己的解答：

public String countAndSay(int n) {
        if (n == 1) {
        	return "1";
        } 
        String str = countAndSay(n-1);
        StringBuilder sb = new StringBuilder();
        int i, count;
        for (i = 1; i < str.length(); i++) {
        	count = 0;
        	while (i == 0 || (i < str.length() && str.charAt(i) == str.charAt(i-1))) {
        		count++;
        		i++;
        	}
        	sb.append(count);
        	sb.append(str.charAt(i-1));
        }
        return sb.toString();
    }

见到一个比较好的解答：

public String countAndSay(int n) {
            StringBuilder curr=new StringBuilder("1");
            StringBuilder prev;
            int count;
            char say;
            for (int i=1;i<n;i++){
                prev=curr;
                curr=new StringBuilder();       
                count=1;
                say=prev.charAt(0);

                for (int j=1,len=prev.length();j<len;j++){
                    if (prev.charAt(j)!=say){
                        curr.append(count).append(say);
                        count=1;
                        say=prev.charAt(j);
                    }
                    else count++;
                }
                curr.append(count).append(say);
            }                   
            return curr.toString();

    }

程序的目的就是为了模拟现实，把手动计算计算机化，就基本是一段不错的思路。。。比较上面的代码，先记录say的数字，然后count，不错。。。。

写代码就是为了模拟现实。。。