算法笔记练习 6.4 map 问题 A: 【PAT A1071】Speech Patterns

算法笔记练习 题解合集

本题链接

题目

题目描述
People often have a preference among synonyms of the same word. For example, some may prefer “the police”, while others may prefer “the cops”. Analyzing such patterns can help to narrow down a speaker’s identity, which is useful when validating, for example, whether it’s still the same person behind an online avatar.

Now given a paragraph of text sampled from someone’s speech, can you find the person’s most commonly used word?

输入
Each input file contains one test case. For each case, there is one line of text no more than 1048576 characters in length, terminated by a carriage return ‘\n’. The input contains at least one alphanumerical character, i.e., one character from the set [0-9 A-Z a-z].

输出
For each test case, print in one line the most commonly occurring word in the input text, followed by a space and the number of times it has occurred in the input. If there are more than one such words, print the lexicographically smallest one. The word should be printed in all lower case. Here a “word” is defined as a continuous sequence of alphanumerical characters separated by non-alphanumerical characters or the line beginning/end.

Note that words are case insensitive.

样例输入

Can1: "Can a can can a can?  It can!"

样例输出

can 5

思路

题目不难，需要注意一些细节：

• 最后一个单词不要忘了统计；
• 不要统计空字符串；
• 注意大小写不敏感，所以统计之前要对字符串作小写化处理。

代码

参考柳神的代码

#include 
#include 
#include 
#include 
using namespace std;
int main() {
	string input, word, maxWord;
	while (getline(cin, input)) { 
		int p = 0, maxCnt = 0;
		map<string, int> wordCnt;
		for (int i = 0; i < input.size(); ++i) {
			if (isalnum(input[i]))
				word += tolower(input[i]);
			if (i == input.size() - 1 || !isalnum(input[i])) {
				if (!word.empty())
					++wordCnt[word];
				word.clear();
			} 
		}
		for (auto it = wordCnt.begin(); it != wordCnt.end(); ++it) {
			if (it->second > maxCnt) {
				maxCnt = it->second;
				maxWord = it->first;
			} 
		}
		cout << maxWord << " " << maxCnt;
	}
	return 0;
} 

自己写的

#include 
#include 
#include 
#include 
using namespace std;
string getWord(const string &input, int &p) {
	string word;
	while (p != input.size() && !isalnum(input[p]))
		++p;
	if (p == input.size())
		return word;
	int begin = p;
	while (p != input.size() && isalnum(input[p]))
		++p;
	word = input.substr(begin, p - begin);
	for (auto &ch : word)
		ch = tolower(ch); 
	return word;
} 
int main() {
	string input, word, maxWord;
	while (getline(cin, input)) { 
		int p = 0, maxCnt = 0;
		map<string, int> wordCnt;
		while (p != input.size()) {
			word = getWord(input, p);
			if (!word.empty()) {
				if (wordCnt.count(word))
					++wordCnt[word];
				else
					wordCnt[word] = 1;
			}
		}
		for (auto it = wordCnt.rbegin(); it != wordCnt.rend(); ++it) {
			if (it->second >= maxCnt) {
				maxCnt = it->second;
				maxWord = it->first;
			} 
		}
		cout << maxWord << " " << maxCnt;
	}
	return 0;
}