计算文本文件中的单词数，C++

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <unordered_map>

using namespace std;

int countWords(const string& filename) {
    ifstream file(filename);
    if (!file.is_open()) {
        cout << "Failed to open file." << endl;
        return 0;
    }

    unordered_map<string, int> wordCount;

    string line;
    while (getline(file, line)) {
        stringstream ss(line);
        string word;
        while (ss >> word) {
            // 去除标点符号
            word.erase(remove_if(word.begin(), word.end(), ::ispunct), word.end());
            // 将单词转为小写
            transform(word.begin(), word.end(), word.begin(), ::tolower);
            // 统计单词数量
            wordCount[word]++;
        }
    }

    file.close();

    int totalWords = 0;
    for (const auto& pair : wordCount) {
        totalWords += pair.second;
    }

    return totalWords;
}

int main() {
    string filename = "example.txt";
    int wordCount = countWords(filename);
    cout << "Total words: " << wordCount << endl;

    return 0;
}