如何用另一个字符串替换一个字符串的所有实例？

我在另一个堆栈问题上发现了这一点：

//http://stackoverflow.com/questions/3418231/c-replace-part-of-a-string-with-another-string
//
void replaceAll(std::string& str, const std::string& from, const std::string& to) {
    size_t start_pos = 0;
    while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        size_t end_pos = start_pos + from.length();
        str.replace(start_pos, end_pos, to);
        start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
    }
}

和我的方法：

string convert_FANN_array_to_binary(string fann_array)
{
    string result = fann_array;
    cout << result << "\n";
    replaceAll(result, "-1 ", "0");
    cout << result << "\n";
    replaceAll(result, "1 ", "1");
    return result;
}

对于这个输入：

cout << convert_FANN_array_to_binary("1 1 -1 -1 1 1 ");

现在，输出应该是“110011”

这是该方法的输出：

1 1 -1 -1 1 1  // original
1 1 0 1  // replacing -1's with 0's
11 1  // result, as it was returned from convert_FANN_array_to_binary()

我一直在查看replaceAll代码，并且，我真的不确定为什么它用一个0替换连续的-1，然后在最终结果中不返回任何0（和一些1）。 =\

完整代码：

std::string ReplaceString(std::string subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();
    }
    return subject;
}

如果您需要性能，这里有一个更优化的函数，它修改输入字符串，它不会创建字符串的副本：

void ReplaceStringInPlace(std::string& subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();
    }
}

Tests:

std::string input = "abc abc def";
std::cout << "Input string: " << input << std::endl;

std::cout << "ReplaceString() return value: " 
          << ReplaceString(input, "bc", "!!") << std::endl;
std::cout << "ReplaceString() input string not changed: " 
          << input << std::endl;

ReplaceStringInPlace(input, "bc", "??");
std::cout << "ReplaceStringInPlace() input string modified: " 
          << input << std::endl;

Output:

Input string: abc abc def
ReplaceString() return value: a!! a!! def
ReplaceString() input string not changed: abc abc def
ReplaceStringInPlace() input string modified: a?? a?? def