C++统计字符串中字符出现次数的方法

#include <iostream>
#include <string>
using namespace std;

int countChar(const string& str, char target) {
    int count = 0;
    for (char c : str) {
        if (c == target) {
            count++;
        }
    }
    return count;
}

int main() {
    string s = "hello world";
    char ch = 'l';
    cout << "字符 '" << ch << "' 出现了 " << countChar(s, ch) << " 次" << endl;
    return 0;
}

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int main() {
    string s = "programming";
    char ch = 'g';
    int count = std::count(s.begin(), s.end(), ch);
    cout << "字符 '" << ch << "' 出现了 " << count << " 次" << endl;
    return 0;
}

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int countCharIgnoreCase(const string& str, char target) {
    int count = 0;
    char lowerTarget = tolower(target);
    for (char c : str) {
        if (tolower(c) == lowerTarget) {
            count++;
        }
    }
    return count;
}