单词统计

#include <iostream>
#include <sstream>
#include <unordered_map>
#include <vector>
#include <algorithm>

int main() {
    std::string line, word;
    std::unordered_map<std::string, int> wordCounts;

    // 读取输入的单词并更新频率计数
    while (getline(std::cin, line) && !line.empty()) {
        std::stringstream ss(line);
        while (ss >> word) {
            // 将单词转换为小写
            for (auto& ch : word) {
                ch = std::tolower(ch);
            }
            ++wordCounts[word];
        }
    }

    std::vector<std::pair<std::string, int>> wordVec(wordCounts.begin(), wordCounts.end());
    // 自定义排序规则
    std::sort(wordVec.begin(), wordVec.end(),
              [](const auto& a, const auto& b) {
                  if (a.second != b.second)
                      return a.second > b.second;
                  else
                      return a.first < b.first;
              });

    // 输出单词种类
    std::cout << wordCounts.size() << std::endl;
    // 输出前五个最高频的单词
    int count = 0;
    for (const auto& pair : wordVec) {
        if (count++ >= 5) break;
        std::cout << pair.first << " " << pair.second << std::endl;
    }

    return 0;
}