【LeetCode从零单排】No38.CountAndSay

本文详细解析了TheCount-and-Say序列的生成逻辑及实现代码，通过实例展示了如何利用循环和字符串操作来生成指定位置的序列。

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题目

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.

代码

public  String countAndSay(int n){
        String lastNum  = "1";
        for(int i  = 1; i <= n - 1 ; i++){
            StringBuilder sb = new StringBuilder();
            char[] chars = lastNum.toCharArray();
            char cur = chars[0];
            int times = 0;
            for(int j = 0; j < lastNum.length(); j++){
                if(chars[j] == cur)
                    times ++;
                else {
                    sb.append(times).append(cur);
                    cur = chars[j];
                    times = 1;
                }
                if(j == lastNum.length() - 1){
                    sb.append(times).append(cur);
                }
            }
            lastNum = sb.toString();
        }
        return lastNum;
    }

代码下载：https://github.com/jimenbian/GarvinLeetCode

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