编辑代码

#include <iostream>
#include <string>

std::string replaceSpaces(const std::string& str) {
    std::string result;  

    for (char c : str) {
        if (c == ' ') {
            result += "%20";  
        } else {
            result += c;     
        }
    }

    return result;  
}

int main() {
    std::string input = "We are happy.";
    std::string output = replaceSpaces(input);
    std::cout << "输出: " << output << std::endl;
    return 0;
}