leetcode由易入难——【6】Count and Say

最新推荐文章于 2023-02-25 23:03:36 发布

anyien

最新推荐文章于 2023-02-25 23:03:36 发布

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分类专栏： Leetcode 文章标签： string

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本文详细解析了TheCount-and-Say序列的生成算法，通过两种方法阐述了如何从给定整数生成第n个序列。包括类定义、方法实现及实例演示。

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.

解法一：

class Solution {
public:
    string countAndSay(int n) {
		string s("1");
		while (--n)
			s = getNext(s);
		return s;
	}
	string getNext(const string s) {
		stringstream ss;
		for (auto i = s.begin(); i != s.end(); ) {
			auto j = find_if(i, s.end(), bind1st(not_equal_to<char>(), *i));
			ss << distance(i, j) << *i;
			i = j;
			}
		return ss.str();
	}
};

解法二：

class Solution {
public:
    string countAndSay(int n) {
        string temp, result;
             result.push_back('1');
        char currentChar;
        int count;
        
        for(int i = 1; i < n; i++) {
            temp = result;
            result.clear();
            currentChar = temp[0];
            
            count = 1;
            for(int j = 1; j < temp.size(); j++) {
                if(temp[j] == currentChar) {
                    count++;
                }
                else {
                    result.push_back('0' + count);
                    result.push_back(currentChar);
                    currentChar = temp[j];
                    count = 1;
                }
            }
            result.push_back('0' + count);
            result.push_back(currentChar);
        }
        return result;
    }
};