Phone Number Divide

最新推荐文章于 2024-10-04 17:35:44 发布

Cindy_zhong

最新推荐文章于 2024-10-04 17:35:44 发布

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本文介绍了一种针对电话号码的分组优化算法，通过将电话号码分为不同类型的小组（优秀、良好、普通），旨在最大化分组的整体质量评分。算法采用递归方式，并通过缓存已计算子序列的质量值来提高效率。

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You are given a String number containing the digits of a phone number (the number of digits, n, can be any positive integer) . To help you memorize the number, you want to divide it into groups of contiguous digits. Each group must contain exactly 2 or 3 digits. There are three kinds of groups:

Excellent: A group that contains only the same digits. For example, 000 or 77.
Good: A group of 3 digits, 2 of which are the same. For example, 030, 229 or 166.
Usual: A group in which all the digits are distinct. For example, 123 or 90.

The quality of a group assignment is defined as 2 × (number of excellent groups) + (number of good groups), Divide the number into groups such that the quality is maximized. Design an e-cient algorithm to return the solution that maximizes the quality.

分析：从头开始扫描phone number，第一个group可以是2或者3个字符，分别计算剩下的序列的quality，最后得到整个序列的最大quality。此处可以使用递归，但是需要注意，可能存在重复计算的情况，可以使用数组来保存已经计算过的子序列的max quality，避免递归时的重复计算。

//返回group的quality值
static int GroupQuality(const char* group, int len){
	assert(len==2 || len==3);
	int quality = 0;
	if (group[0] == group[1]){
		if (len==2 || (len==3&&group[1]==group[2]))
			quality = 2;
		else
			quality = 1;
	} else if (len == 3 && (group[0]==group[2] || group[1]==group[2])){
		quality = 1;
	}
	return quality;
}
//计算phoneNumber的第一个分组字符数为firstGroup时对应的最大quality值和相应分组
static int PhoneNumberQuality(const char* phoneNumber, int numberLen, int firstGroup, int qualities[], string groups[], string& group){
	int quality = -1;
	group = "";
	if (numberLen==firstGroup || numberLen-firstGroup>=2){
		quality = GroupQuality(phoneNumber, firstGroup);
		group = string(phoneNumber, firstGroup);
		if (numberLen-firstGroup>=2){
			PhoneNumberSplit(phoneNumber+firstGroup, numberLen-firstGroup, qualities+firstGroup, groups+firstGroup);
			quality += qualities[firstGroup];
			group += "-"+groups[firstGroup];
		}
	}
	return quality;
}
//递归计算phoneNumber[0..numberLen-1]每个位置对应的最大quality值和相应的分组
static void PhoneNumberSplit(const char* phoneNumber, int numberLen, int qualities[], string groups[]){
	if (qualities[0] >= 0)
		return;
	assert(numberLen>=2);
	int quality = -1;
	string group;
	string tmpGroup;
	//第一个分组时3个字符的情况
	int tmpQuality = PhoneNumberQuality(phoneNumber, numberLen, 3, qualities, groups, tmpGroup);
	if (tmpQuality>quality){
		quality = tmpQuality;
		group = tmpGroup;
	}
	//第一个分组时2个字符的情况
	tmpQuality = PhoneNumberQuality(phoneNumber, numberLen, 2, qualities, groups, tmpGroup);
	if (tmpQuality>quality){
		quality = tmpQuality;
		group = tmpGroup;
	}
	qualities[0] = quality;
	groups[0] = group;
}
//返回电话号码进行分组后的最大Quality值，group返回具有最大Quanlity值得分组
int PhoneNumberSplit(const string& phoneNumber, string& group){
	int numberLen = phoneNumber.length();
	assert(numberLen>=2);
	int* qualities = new int[numberLen];
	memset(qualities, -1, sizeof(int)*numberLen);	//qualities[i]==-1表示第i个字符的quality值尚未计算
	string* groups = new string[numberLen];			//存放qualities对应的分组情况
	PhoneNumberSplit(phoneNumber.c_str(), numberLen, qualities, groups);
	int maxQuality = qualities[0];
	group = groups[0];
	delete[] qualities;
	delete[] groups;
	return maxQuality;
}