您可以使用来自流的格式化输入，而不是std::getline。默认情况下，格式化输入跳过空格：

#include <iostream>
#include <sstream>
int main() {
    std::string s[3] = {"a 1", "b    2", "c  3"};
    for (const auto& str : s) {
        std::istringstream ss(str);
        if (std::string tok; ss >> tok) {
            // at least one token read, print it
            std::cout << tok;
            // then read the rest and prepend them with '.' instead:
            while (ss >> tok) {
                std::cout << '.' << tok;
            }
        }
        std::cout << '\n';
    }
}

输出：

a.1
b.2
c.3

Demo

您可以使用std::regex_replace来实现这一点，除非有特殊的原因需要使用stringstream。

#include <iostream>
#include <iterator>
#include <regex>
#include <string>
int main()
{
    std::string s[3] = {"a 1", "b    2", "c  3"};
    for (std::string& str : s) {
        str = std::regex_replace(str, std::regex{"\\s+"}, ".");
        std::cout << str << std::endl;
    }
    return 0;
}

Output

a.1
b.2
c.3

你可以用我之前写的split函数来实现。

#include <vector>
#include <string_view>
#include <iostream>
// it is always useful to build up a library of functions
// regex as said is awfully slow. And splitting (or tokenizing)
// strings is needed often.
// split uses string_views on the original string
// so keep the original string in memory
//
auto split(std::string_view string, std::string_view delimiters)
{
    std::vector<std::string_view> substrings;
    if ((string.size() == 0ul))
    {
        return substrings;
    }
    if (delimiters.size() == 0ul)
    {
        substrings.emplace_back(string);
        return substrings;
    }
    auto start_pos = string.find_first_not_of(delimiters);
    auto end_pos = start_pos;
    auto max_length = string.length();
    while (start_pos < max_length)
    {
        end_pos = std::min(max_length, string.find_first_of(delimiters, start_pos));
        if (end_pos != start_pos)
        {
            substrings.emplace_back(&string[start_pos], end_pos - start_pos);
            start_pos = string.find_first_not_of(delimiters, end_pos);
        }
    }
    return substrings;
}
// using namespace std; <== do not do this.
int main()
{
    std::vector<std::string> strings{ "a 1", "b    2", "c  3" };
    for (const auto& string : strings)
    {
        // this will split to sets of tokens {"a", "1"}, {"b","2"} and {"c", "3"}
        auto tokens = split(string," ");
        std::cout << "tokens : ";
        // output the (cleaned up) tokens
        for (const auto& token : tokens)
        {
            std::cout << token << " ";
        }
        std::cout << "\n";
    }
    return 0;
}